collaborator

noun

1. someone who assists in a plot

   noun.person

   Synonyms confederate henchman partner in crime

   Source: WordNet 3.0

2. someone who collaborates with an enemy occupying force

   noun.person

   Synonyms collaborationist quisling

   Source: WordNet 3.0

3. an associate in an activity or endeavor or sphere of common interest

   noun.person

   Examples

   The musician and the librettist were collaborators.

   Synonyms cooperator pardner partner

   Source: WordNet 3.0

4. An associate in labor, especially in literary or scientific labor.

   noun

   Source: webster1913