That is “boo,” as in a word used to scare people.
Not the urban dictionary “boo” that refers to a boyfriend or girlfriend.
Nor the “boo” that is uttered or shouted to show contempt, scorn or disapproval.
Not even the “boo” used as an informal word, such as, “You never said ‘boo’ to me about overtime.”
(Did you know the world’s cutest dog is a Pomeranian named Boo?)
Nope, I was working on my scary boo yesterday morning.
Until I realized that I needed a costume that wouldn’t offend anybody.