collaborate

Meanings

1. To work together with others to achieve a common goal.
2. To voluntarily cooperate treasonably, as with an enemy occupation force in one's country.

Etymology

Back-formation from collaborator, from French collaborateur, or else modeled on French collaborer or directly from Late Latin collabōrātus, past participle of collabōrāre. Displaced native Old English efnwyrċan.