Or search: ineradicable
3 Syllables: SUU
fashionable, reasonable
4 Syllables: SUUU
pardonable, questionable, seasonable, serviceable, treasonable
5 Syllables: USUUU
abominable, companionable, determinable, imaginable, impressionable, inalienable, interminable, objectionable, unfashionable, unpardonable, unquestionable, unseasonable
6 Syllables: UUSUUU
unexceptionable

Found 20 words across 4 groupings.