Or search: unbelievingly, disbelievingly
3 Syllables: SUU
desperately, generally, preferably, separately
4 Syllables: SUUU
celibacy, creditably, definitely, delicacy, delicately, generously, marvellously, marvelously, mercilessly, perilously, scrupulously, sedulously, treacherously
4 Syllables: USUU
confederacy
5 Syllables: USUUU
degeneracy, effeminacy, indefinitely, inevitably, inseparably, intelligibly, meticulously, miraculously, professionally, ridiculously
5 Syllables: UUSUU
irrevocably

Found 29 words across 5 groupings.