Or search: unimportant, insignificant
3 Syllables: SUU
amiable, enviable, feasible, malleable, peaceable, permeable, pitiable, readable, reasonable, variable
3 Syllables: UUS
agreeable, foreseeable
4 Syllables: USUU
amenable, appreciable, conceivable, invariable, unenviable, unreasonable, unspeakable
4 Syllables: UUUS
disagreeable
5 Syllables: UUSUU
inconceivable, irremediable, irretrievable, unbelievable, unimpeachable

Found 25 words across 5 groupings.