WR has about 6,000 rhymes for "smarter" starting with...

arter
    barter
      carter
        charter
          darter
            garter
              martyr
                starter
                  nonstarter
                    Karter
                      Sartor
                        Tartar
                          Tarter
                            Pure Rhyme Set #1 of 1 (Add to/Edit Set Members)
                            Words that have a pure rhyme on their last syllable only.
                            partner
                              Gartner
                                End Rhyme Set #1 of 576 (Add to/Edit Set Members)
                                Arthur
                                  MacArthur
                                    McArthur
                                      End Rhyme Set #2 of 576 (Add to/Edit Set Members)
                                      armer
                                        armor
                                          armour
                                            charmer
                                              farmer
                                                Harmer
                                                  Marmor
                                                    • knight in shining armour
                                                    End Rhyme Set #3 of 576 (Add to/Edit Set Members)

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                                                    Words that "almost" rhyme on the vowel-based rhyme sound of the stressed syllable like: be/eat or maybe/shapely. (Click for more info)
                                                    partner
                                                      Gartner
                                                        Near Rhyme Set #1 of 60 (Add to/Edit Set Members)
                                                        Arthur
                                                          MacArthur
                                                            McArthur
                                                              Near Rhyme Set #2 of 60 (Add to/Edit Set Members)
                                                              armer
                                                                armor
                                                                  armour
                                                                    charmer
                                                                      farmer
                                                                        Harmer
                                                                          Marmor
                                                                            • knight in shining armour
                                                                            Near Rhyme Set #3 of 60 (Add to/Edit Set Members)

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                                                                            Rhymes made up of more than one word. For instance, "jealous" and "tell us" or "shaky" and "make me."
                                                                            • afar + her
                                                                            • afar + were
                                                                            • ar + her
                                                                            • ar + were
                                                                            • are + bur
                                                                            • are + cur
                                                                            • are + der
                                                                            • are + fer
                                                                            • are + fir
                                                                            • are + fur
                                                                            • are + her
                                                                            • are + mer
                                                                            • are + per
                                                                            • are + pur
                                                                            • are + sir
                                                                            • are + spur
                                                                            • are + stir
                                                                            • are + sur
                                                                            • are + ter
                                                                            • are + ur
                                                                            • are + were
                                                                            • bar + her
                                                                            • bar + per
                                                                            • bar + were
                                                                            • Barr + were
                                                                            • bazaar + were
                                                                            • bizarre + were
                                                                            • car + her
                                                                            • car + per
                                                                            • car + were
                                                                            • Carr + were
                                                                            • char + ter
                                                                            • cigar + were
                                                                            • clar + ter
                                                                            • dar + fer
                                                                            • dar + ter
                                                                            • far + der
                                                                            • far + err
                                                                            • far + her
                                                                            • far + mer
                                                                            • far + per
                                                                            • far + sur
                                                                            • far + ter
                                                                            • far + were
                                                                            • Farrar + were
                                                                            • gar + her
                                                                            • gar + were
                                                                            • guitar + were
                                                                            • har + ter
                                                                            • jar + her
                                                                            • jar + were
                                                                            • Lamar + were
                                                                            • Maher + were
                                                                            • mar + her
                                                                            • mar + per
                                                                            • Mawr + were
                                                                            • Meagher + were
                                                                            • Myanmar + were
                                                                            • Navarre + were
                                                                            • our + cur
                                                                            • our + der
                                                                            • our + fir
                                                                            • our + fur
                                                                            • our + her
                                                                            • our + mer
                                                                            • our + per
                                                                            • our + pur
                                                                            • our + sir
                                                                            • our + spur
                                                                            • our + stir
                                                                            • our + sur
                                                                            • our + ter
                                                                            • our + ture
                                                                            • our + ur
                                                                            • our + were
                                                                            • par + mer
                                                                            • par + per
                                                                            • par + were
                                                                            • Parr + were
                                                                            • Qatar + were
                                                                            • r + der
                                                                            • r + fur
                                                                            • r + her
                                                                            • r + per
                                                                            • r + ter
                                                                            • r + ture
                                                                            • r + ur
                                                                            • r + were
                                                                            • Renoir + were
                                                                            • Saar + were
                                                                            • sar + were
                                                                            • scar + her
                                                                            • scar + were
                                                                            • spar + were
                                                                            • star + her
                                                                            • star + per
                                                                            • star + were
                                                                            • Starr + were
                                                                            • tar + her
                                                                            • tar + per
                                                                            • tar + were
                                                                            • thar + fer
                                                                            • thar + fur
                                                                            • thar + ter
                                                                            • thar + were
                                                                            • victoire + sur
                                                                            • voir + sur
                                                                            Mosaic Rhyme Set #1 of 1 (Add to/Edit Set Members)