partisan noun (1)
par·​ti·​san | \ˈpär-tə-zən, -sən, -ˌzan, chiefly British ˌpär-tə-ˈzan \
variants: or less commonly partizan
Definition of partisan (Entry 1 of 3)
1 : a firm adherent to a party, faction, cause, or person
especially : one exhibiting blind, prejudiced, and unreasoning allegiance
political partisans who see only one side of the problem
2a : a member of a body of detached light troops making forays and harassing an enemy
Peasant partisans assaulted the French army.
b : a member of a guerrilla band operating within enemy lines