Here's what rhymes with threefifth.
fifth Words that almost rhyme with threefifth
sieves scythes riffs skiffs sniffs whiffs stiffs gives lives myths cliffs smiths writhes clefs relives withes forgives mastiffs hieroglyphs blacksmiths goldsmiths silversmiths monoliths filth scythe myth sixth width pith smith writhed writhe plinth hyacinth forthwith labyrinth therewith herewith wherewith silversmith monolith