a shop, business establishment, or part thereof, in which terms and conditions of employment for all employees are fixed by agreement between the employer and a labor union.
2.
a shop, business, etc., in which membership in a union is made a condition of employment, but in which the employer may hire nonunion workers provided that they become members after a stated period, usually 30 days.
(formerly) an establishment whose employment policy is governed by a contract between employer and a trade union permitting the employment of nonunion labour only on the condition that such labour joins the union within a specified time period Compare open shop, closed shop