collaborator
//kəˈlæbəˌreɪtər//
Noun
collaboratorSingular
collaboratorsPlural
1
A person who works jointly with others, especially in an intellectual or creative endeavor.
She has been my collaborator on several research projects.
2
A person who cooperates traitorously with an enemy, especially an occupying force.
After the war, collaborators who had helped the enemy were put on trial.