Or search: credibly, plausibly
2 Syllables: SU
theory
3 Syllables: SUU
cheerily, deities, deity, dreamily, easily, equally, gleefully, greedily, grievously, guillotine, legally, mediately, needlessly, peaceably, plenary, scenery, secrecy, speedily, tyranny, zealously
3 Syllables: USU
machinery, serenely
3 Syllables: UUS
agreeably
4 Syllables: USUU
appreciably, conceivably, conspiracy, illegally, immediately, obesity, supremely, uneasily, unequally, unspeakably
4 Syllables: UUUS
disagreeably, spontaneity
5 Syllables: UUSUU
inconceivably, irretrievably
5 Syllables: UUUUS
homogeneity
6 Syllables: UUUUUS
heterogeneity

Found 40 words across 9 groupings.