Boo is a versatile slang term with multiple meanings depending on context:
1. As a term of endearment: "Boo" is commonly used to refer to one's romantic partner, similar to "baby" or "honey".
2. As an expression of disapproval: When shouted at performances or events, "Boo!" conveys dissatisfaction or contempt.
3. In Halloween context: "Boo" is an onomatopoeia representing the sound of a ghost.
4. In gaming: "Boo" refers to the ghost enemies in the Mario franchise.
5. As a verb: To "boo" someone means to express disapproval by shouting "boo".