What does BOO mean??

A.S.C.M,

I also knew that meaning. Before posting I had some sort of fishy feeling whether it was only 'boo' or 'boo-boo'.

I did not want to be a know-it-all , and gave a chance to other smart-heads. So, you were a smart-head eventually.

''Boo boo'' is slang for a mistake

''boo'' is what a ghost says or what people say to scare other people.