spook

A ghost or phantom.informal

• The building was haunted by a couple of spooks.

A scare or fright.informal

• The big spider gave me a spook.

An undercover agent, spy, or intelligence analyst.slang

• From Ian Fleming to John Le Carre - authors have long been fascinated by the world of espionage. But, asks the BBC’s Gordon Corera, what do real life spooks make of fictional spies?
• The congressional study frets that Huawei’s and ZTE’s products could be used as Trojan horses by Chinese spooks.

A black person.datedethnicoffensive

• Some won't take spooks—hell, don't make no difference to me.
• "[…] Dryades Street and that whole uptown neighborhood is gonna be worth a fortune once the white people take it back from you spooks and develop it. […]"

A metaphysical manifestation; an artificial distinction or construct.

• He who is infatuated with Man leaves persons out of account so far as that infatuation extends, and floats in an ideal, sacred interest. Man, you see, is not a person, but an ideal, a spook.

A psychiatrist.USslang

• Commonly, the surgeons view nonsurgeons with disdain. The most disdain is directed toward the “shrinks” or the “spooks,” as the psychiatrists are called.

A player who engages in hole carding by attempting to glimpse the dealer's hole card when the dealer checks under an ace or a 10 to see if a blackjack is present.slang

To frighten or make nervous (especially by startling).transitive

• The hunters were spooked when the black cat crossed their path. The movement in the bushes spooked the deer and they ran.

To become frightened (by something startling).intransitive

• The deer spooked at the sound of the dogs.

To haunt.transitive