mil·i·tant 
(mĭlĭ-tənt)
(mĭlĭ-tənt)adj.
1. Fighting or warring.
2. Having a combative character; aggressive, especially in the service of a cause: a militant political activist.
n.
A fighting, warring, or aggressive person or party.
[Middle English, from Old French, from Latin mīlitāns, mīlitant-, present participle of mīlitāre, to serve as a soldier; see MILITATE.]
mili·tance, mili·tan·cy n.
mili·tant·ly adv.