What does the term "closed shop" signify in a labor context?

The term "closed shop" in a labor context signifies an operation where only union members can be hired. This means that, in order to gain employment at a closed shop, workers must first be a member of the union. This arrangement is designed to ensure that all employees adhere to union standards and regulations, promoting collective bargaining and protecting workers' rights.

In environments with a closed shop, the union typically has significant influence over the hiring process and can limit job opportunities to non-union workers. This is often viewed as a way to strengthen the union's bargaining power and ensure that all employees receive the benefits that the union negotiates.

The other options refer to different contexts of union involvement but do not accurately represent what a closed shop entails. For instance, encouraging workers to join unions or allowing temporary union membership represents a more flexible relationship between workers and unions, while a fully nonunion operation describes a situation where no union representation exists at all, which contrasts with the exclusivity defined by a closed shop.