Or search: acceptable, unimpeachable
3 Syllables: SUU
fashionable, reasonable
4 Syllables: SUUU
pardonable, questionable, reputable, seasonable, treasonable
5 Syllables: USUUU
abominable, companionable, determinable, disreputable, imaginable, impressionable, inalienable, inexorable, interminable, objectionable, unfashionable, unpardonable, unquestionable, unseasonable

Found 21 words across 3 groupings.