Definitions
1.nounA soldier, a combatant.
2.nounAn entrenched or aggressive adherent to a particular cause, now especially a member of a particular ideological faction.
3.nounSpecifically, someone who supports the Trotskyist political view expressed in the newspaper Militant, or who engages in aggressive left-wing politics.
4.adjectiveFighting or disposed to fight; belligerent, warlike.
5.adjectiveAggressively supporting of a political or social cause; adamant, combative.