Superlative form of spooky: most spooky.(adjective)
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Use "spookiest" in a sentence
"The shot of whatever it was getting up and walking toward her was the spookiest image on the show to date."
"And whilst I admit I live in what looks to be the spookiest house on the street, surely that should be a bonus attraction on Halloween?"
"If you've ever wondered about the year's spookiest day beyond the costumes and candy, "The Real Story of Halloween" (History at 8) looks at the true origins of the Oct. 31 holiday."