Spook
noun
noun: spook; plural noun: spooks

1.
informal
a ghost.
2.
informal•North American
a spy.
"a CIA spook"
3.
offensive•dated
a black person.

verbinformal
verb: spook; 3rd person present: spooks; past tense: spooked; past participle: spooked; gerund or present participle: spooking

frighten; unnerve.
"they spooked a couple of grizzly bears"
(especially of an animal) take fright suddenly.
"he'll spook if we make any noise"