Bo \Bo\, interj. [Cf. W. bw, an interj. of threatening or frightening; n., terror, fear, dread.] An exclamation used to startle or frighten. [Spelt also {boh} and {boo}.]
boo \boo\ v. to show displeasure (after a performance or speech) by making a prolonged sound of ``boo''. [WordNet 1.5]
At the official rally at which Ceausescu spoke, hundreds of people began to boo and jeer, and thousands more soon joined in, Tomic journalist said.
Whenever its four professional sports teams fail to measure up, the home crowd is sure to boo mercilessly.
They said, "I do," but they could have said, "I boo," too.
Chicago sports fans may not boo with the resonance of Philadelphians, throw batteries with the accuracy of New Yorkers or exit parking lots with the swiftness of Angelenos, but we take a back seat to no one when it comes to carping.