(n.) A mate; a partner; esp., an accomplice or confederate.

ace amigo associate associate with assort with bedfellow bedmate bosom buddy buddy bunkie bunkmate butty camarade chamberfellow chum chum together chum with classmate clique clique with club together colleague comate companion company compeer comrade confrere consociate consort consort with copartner crony fellow fellow student fellowship flock together fraternize girl friend gossip hang around with hang out with herd together hobnob with join join in fellowship keep company with mate messmate mingle with mix with old crony pal up with pal with pard pardner partner playfellow playmate roommate run run in couples run with schoolfellow schoolmate shipmate side partner sidekick sort with take up with teammate tie up with workfellow yokefellow yokemate