'Spook' definitions:

Definition of 'spook'

(from WordNet)
noun
Someone unpleasantly strange or eccentric [syn: creep, weirdo, weirdie, weirdy, spook]
noun
A mental representation of some haunting experience; "he looked like he had seen a ghost"; "it aroused specters from his past" [syn: ghost, shade, spook, wraith, specter, spectre]
verb
Frighten or scare, and often provoke into a violent action; "The noise spooked the horse"

Definition of 'Spook'

From: GCIDE
  • Spook \Spook\ (sp[=oo]k), n. [D. spook; akin to G. spuk, Sw. sp["o]ke, Dan. sp["o]gelse a specter, sp["o]ge to play, sport, joke, sp["o]g a play, joke.]
  • 1. A spirit; a ghost; an apparition; a hobgoblin. [Written also spuke.] --Ld. Lytton. [1913 Webster]
  • 2. (Zool.) The chimaera. [1913 Webster]

Synonyms of 'spook'

From: Moby Thesaurus