radical

[1]	group , chemical group
[2]	free radical
[3]	extremist , revolutionary , fanatic , zealot , immoderate , anarchist , militant
[4]	communist , leftist , left-winger , red , Bolshevik , Bolshevist , pink , (Slang) (US) pinko
[5]	root , root word , base , stem , theme

adj.

[1]	basic , fundamental , elementary , inherent , constitutional , elemental , essential , cardinal , principal , primary , deep , deep-seated , profound , underlying , organic , natural , rudimentary
[2]	thorough , thoroughgoing , complete , entire , total , exhaustive , sweeping , (all-)inclusive , comprehensive , all-embracing , out-and-out , drastic , severe , extreme , extremist , revolutionary
[3]	extremist , revolutionary , fanatic(al) , militant , anarchist(ic) , immoderate
[4]	extremist , ultra
[5]	revolutionary
[6]	basal