Or search: oceanic, boundless, unbounded, unlimited, unmeasured, untrammeled, illimitable, measureless, unmeasurable, untrammelled
2 Syllables: SU
Nicholas
3 Syllables: SUU
bitterest, frivolous, impetus, incubus, minuteness, rigorous, Spiritus, syllabus, timorous, vigorous, villainous
4 Syllables: USUU
antithesis, carnivorous, felicitous, indigenous, solicitous, vociferous
5 Syllables: UUSUU
abolitionist

Found 19 words across 4 groupings. Skipped 1 excess word of a similar stem.