Or search: iridescent
2 Syllables: SU
buoyant, moisten, noisome, ointment, poignant, poison, toilsome
3 Syllables: USU
annoyance, appointment, avoidance, deployment, employment, enjoyment, flamboyant
4 Syllables: UUSU
disappointment, unemployment

Found 16 words across 3 groupings. Skipped 8 excess words of a similar stem.