Smartened rhymes with:
disheartened, heartened, disheartened, heartened, shortened, brightened, buttoned, cottoned, disheartened, enlightened, fattened, flattened, frightened, heartened, heightened, heistand, hestand, hiestand, lightened, montand, predestined, shortened, straightened, sweetened, threatened, tightened, unbuttoned, unenlightened