A loud exclamation intended to scare someone, especially a child. Usually used when one has been hidden from the victim and then suddenly appeared unexpectedly
a name given to a recluse, or someone strange and antisocial, as in Boo Radley from To Kill A Mockingbird: "Watch out for Boo; he might be a serial killer"
an expression used when someone stares at you for a long time and doesn't speak to you; you say boo!! "I said boo to that guy who just stared at me in the library"
A word used by someone who is inherently scary, such as a ghost or a vampire, to make a weaker person who is scared stiff flee. Usually used quietly, as with definition 2
You say `Boo!' loudly and suddenly when you want to surprise someone who does not know that you are there. see also peekaboo. to shout 'boo' to show that you do not like a person, performance, idea etc
If you boo a speaker or performer, you shout `boo' or make other loud sounds to indicate that you do not like them, their opinions, or their performance. People were booing and throwing things at them Demonstrators booed and jeered him He was booed off the stage. Boo is also a noun. She was greeted with boos and hisses. + booing boo·ing The fans are entitled to their opinion but booing doesn't help anyone