collaborator
col-lab-o-ra-tor
noun
A person who works jointly with others on a project or task.
"She was a key collaborator on the research paper."
noun
Someone who cooperates traitorously with an enemy occupying their country.
"He was branded a collaborator during the war."
Thesaurus
Synonyms: pardner, cooperator, partner, partner in crime, confederate, quisling, collaborationist