Behaving as an activist.
One who is politically active in the role of a citizen; especially, one who campaigns for change.
One who is conspicuously active in carrying out any occupational or professional functions.
Aggressively supporting of a political or social cause; adamant, combative.
Fighting or disposed to fight; belligerent, warlike.
Specifically, someone who supports the Trotskyist political view expressed in the newspaper Militant, or who engages in aggressive left-wing politics.
An entrenched or aggressive adherent to a particular cause, now especially a member of a particular ideological faction.