Other forms: spooks, spooked, spooking
To spook is to frighten somebody suddenly. Spook the horses, it spooked him, easily spooked.
It is most used of animals, especially horses, which spook at a plastic bag and not at a lorry. Of markets it means to cause sudden nervous selling: the announcement spooked investors. As a noun, a spook is a ghost, and in American use also a spy — which is why the British television series about the security service was called Spooks. Note spooky, meaning eerie, which is now the commonest form of all.
1verbspookTo frighten somebody suddenly.
“Something spooked the horse at about the fourth fence.”
synonyms: startle, scare
2nounghostA ghost, or informally a spy.
“The children swore the old house was full of spooks.”
spook is a frightening, or a ghost.
Also accepted in games: startle
Dutch spook means a ghost, and English borrowed it in the nineteenth century through American usage. The verb came from the noun: to spook was to haunt before it was to frighten.
Middle Dutch
spooc — spook, ghost
Dutch
spook — ghost
English, today
spook
Borrowed from Dutch spook (“ghost”), from Middle Dutch spooc (“spook, ghost”). Cognate with Middle Low German spôk, spûk (“apparition, ghost”), Middle High German gespük (“a haunting”), German Spuk, Danish spøge (“to haunt”), Swedish spöke (“ghost”).
Etymology from Wiktionary, CC BY-SA
Practised in A Song of Ice and Fire