Adjective

1. aggressive or combative
2. fighting or warlike; belligerent
3. Active in an aggressive way in support of a political or social cause (often associated with extreme left-wing politics).

Noun

1. an aggressive or fighting person
   • 2008, Militants in Pakistan release 250 schoolchildren after taking them hostage, Wikinews:

     Officials in Pakistan have confirmed that at least 250 schoolchildren between 12 and 18 years old and several teachers were taken hostage by at least seven militants inside a high school in Domail.

2. one who serves as a soldier
3. one who supports a Trotskyite political view or engages in aggressive left-wing politics.