Brooks are afraid of girls, they Brook out when one talks to them. Usually when a girl says hey to a Brook, a Brook will respond by saying something gay like 'yo'. People who wish to bring someone out who acts like this will say 'don't be a Brook'.
Nobody wants to be a Brook.
A Brook: Looks away and mumbles 'yo'.
Oh dude look. She is such a Brook. Look at the way Stacie watches her.