A lockout is a work stoppage or denial of employment initiated by the management of a company during a labor dispute). Unlike a strike, which is initiated by employees refusing to work, a lockout is initiated by employers or industry owners). Lockouts are usually implemented by simply refusing to admit employees onto company premises, and may include changing locks or hiring security guards for the premises). Lockouts are often used to force unionized workers to accept new conditions, such as lower wages, or to enforce specific terms of employment upon a group of employees during a dispute. Lockouts are common in major league sports, many of which operate as legalized cartels). The National Football League, Major League Baseball, the National Basketball Association, and the National Hockey League have all experienced lockouts).

In the context of workplace safety, lockout refers to the de-energizing and securing of equipment, machinery, or processes so hazardous energy isnt re-introduced during servicing or repair. The OSHA lockout tagout standard for the Control of Hazardous Energy (Lockout/Tagout) was developed in 1982 by the United States Occupational Safety and Health Administration (OSHA) to help protect workers who routinely service equipment in the workplace. Legally, it went into effect in 1989. Lockout occurs when an energy source (electrical, mechanical, hydraulic, pneumatic, chemical, thermal, or other) is physically isolated from the system that uses it (a machine, equipment, or process). This is done using a variety of lockout padlocks and devices best suited for specific applications.