Or search: fun, sober, sedate, solemn, sincere, grievous, sobering, sincerity, unplayful, thoughtful, earnestness
2 Syllables: SU
bilious, busiest, clearness, dearest, devious, easiest, eras, fearless, fiercest, hideous, idiots, nearest, nearness, peerage, piteous, prettiest, previous, tedious, Theseus, vitreous
3 Syllables: SUU
dizziness, giddiness, greediness, pitiless, weariness
3 Syllables: USU
abstemious, amphibious, Aurelius, delirious, Demetrius, Eusebius, fastidious, imperious, initiates, insidious, invidious, lascivious, Mauritius, mysterious, oblivious, obsequious, perfidious, Prometheus, punctilious, severest, sincerest, Tiberius
4 Syllables: USUU
uneasiness
4 Syllables: UUSU
deleterious, Dionysius, homogeneous, ignominious, supercilious

Found 53 words across 5 groupings.