plural of sleeper agent

A spy who is placed in a target country or organisation, not to undertake an immediate mission, but rather to act as a potential asset if activated.

plural of rough sleeper

(idiomatic, euphemistic) A homeless person who sleeps outdoors.

plural of sleeper cab

plural of sleeplessness

plural of railway sleeper

plural of sleeper ship

(science fiction) A spaceship, all or some of whose passengers are in suspended animation.

plural of sleepiness