Or search: fascism, naziism, socialism
3 Syllables: SUU
Addison, Addison's, Africans, aliment, Alison, Allison, applicant, chastisement, Fascism, garrison, Madison, talisman, Vatican
4 Syllables: USUU
inhabitant, Mohammedan

Found 15 words across 2 groupings. Skipped 2 excess words of a similar stem.