n.
Pronunciation: ' ə l-tr ə - ˌ i-z ə m
Function: noun
Date: 1821
1 : the principles of those who advocate extreme measures (as radicalism)
2 : an instance or example of radicalism
– ul · tra · ist \ -tr ə -ist \ adjective or noun
– ul · tra · is · tic \ ˌ ə l-tr ə - ' is-tik \ adjective