Someone who collaborates with an enemy occupying force.

synonyms: collaborationist, collaborator.

Roget 742: disobedience, insubordination, contumacy; infraction, infringement; violation, noncompliance; nonobservance etc. 773.    revolt, rebellion, mutiny, outbreak, rising, uprising, insurrection, emeute [Fr.]; riot, tumult etc. (disorder) 59; strike etc. (resistance) 719; barring out; defiance etc. 715.    mutinousness etc. adj.; mutineering^†; sedition, treason; high treason, petty treason, misprision of treason; premunire [Lat.]; lese majeste [Fr.]; violation of law etc. 964; defection, secession.    insurgent, mutineer, rebel, revolter, revolutionary, rioter, traitor, quisling, carbonaro^†, sansculottes [Fr.], red republican, bonnet rouge, communist, Fenian, frondeur; seceder, secessionist, runagate, renegade, brawler, anarchist, demagogue; Spartacus, Masaniello, Wat Tyler, Jack Cade; ringleader.    ... show more

Dutch: collabo, collaborateur, landverrader, quisling
Polish: kolaboracjonista, kolaborant