Entry 1 sense Webster, 1913 co-worker /(k?`w?rk"?r)/ · co·-work·er · IPA /kˈoʊwˈɜrkər/ 01 n. One who works with another; a cooperator. 1. One who works with another; a cooperator. Syn. colleague, coworker, fellow worker, fellow-worker, workfellow.