A group of people (sleepers) who inconspicuously remain dormant in a community until activated, by a prearranged signal, to perform acts of espionage, sabotage, and/or terrorism.

plural of sleeper agent

plural of rough sleeper

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.

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

plural of railway sleeper

plural of sleeper ship

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

Any of the genus Eleotris of sleeper gobies with a circumglobal distribution in tropical and subtropical regions.

plural of spinycheek sleeper