Politically radical

Wiktionary Word definitions in Wiktionary
n. 1 (context politics English) the more left-wing faction of a group or party 2 (context sports English) the left-hand side of a sports field 3 (context ice hockey English) the offensive player who plays to the center's left

The Collaborative International Dictionary Word definitions in The Collaborative International Dictionary
left wing \left wing\ n. Those trying to reform the established order, particularly in political matters, to enhance the condition of the common people; -- sometimes applied to those advocating overthrow of an existing government by radical means. Syn: ...

WordNet Word definitions in WordNet
n. those who support varying degrees of social or political or economic change designed to promote the public welfare [syn: left ]

Douglas Harper's Etymology Dictionary Word definitions in Douglas Harper's Etymology Dictionary
also (as an adjective) left-wing , 1871 in the political sense (1530s in a military formation sense), from left (adj.) + wing (n.). Related: Left-winger .