Definition of collaborationist in US English:

collaborationist

adjective

  • Relating to traitorous cooperation with an enemy.

    ‘the discovery of his collaborationist past became an occasion for heated debates’

noun

  • A person who traitorously cooperates with an enemy.

    ‘an accused Nazi collaborationist’

Pronunciation

collaborationist

/kəˌlæbəˈreɪʃ(ə)nəst//kəˌlabəˈrāSH(ə)nəst/