to prevent someone from entering a building or room by locking the door

He had to break into the house because his girlfriend had locked him out. 由于女朋友把他锁在了门外，他只好破门而入。

to prevent workers from entering their place of work until they agree to particular conditions given by the employer

Management has threatened to lock out the workforce if they do not accept the proposed changes in working methods. 管理层威胁说，如果工人不接受改变工作方法的提议就不让他们上班。