A physical membership card carried by active union members, particularly those belonging to the Industrial Workers of the World. On the shop floor, carrying one signifies a worker's commitment to organized labor and collective bargaining. It is often checked by shop stewards to ensure everyone on a closed-shop site is in good standing.
Heard on the job
Check with the steward before you start your shift, he's going to want to see your red card.
Insider tip
Asking to see someone's red card is a classic way to check if a new arrival is union or non-union labor.