Or search: ai, fo, apc, dia, foe, gun, hut, spy, usa, aide, fort, mess, navy, rear, seal
4 Syllables: SUUU
budgetary, cemetery, dietary, dignitary, literary, millinery, missionary, monetary, planetary, Presbytery, salutary, sanitary, secretary, solitary, tributary, unitary, visionary
5 Syllables: USUUU
epistolary, hereditary, itinerary, pituitary, preliminary, proprietary, traditionary
6 Syllables: UUSUUU
expeditionary

Found 25 words across 3 groupings.