1. A guard hired to protect strikebreakers; a scab or strikebreaker; a labor spy. 2. One who comes (to the carnival) not to spend but to find cause for complaint to police. 3. A prison guard. 4. A stool pigeon; an informer. "You can't get around and promote anything (get stolen food and contraband) in this can (prison). The dump is crummy with finks."

- american underworld dictionary - 1950