Eighteen rhymes with:
augustin, canteen, cantin, casteen, chasteen, chretien, christine, cortine, fifteen, foltene, fourteen, gelatine, guertin, justine, kristine, lopatin, martine, muntean, nineteen, o'steen, preteen, routine, seventeen, shasteen, sistine, sixteen, steen, stene, teen, thirteen, umpteen, valentin
Eighteen sounds like:
eastham, eastin, eastman, easton, echidna, eckstein, ecosystem, ecton, ejection, equation, equitation, estan, esteem, estonia, estonian, exaction, excitation, execution, executone, exhaustion, exton, eyestone