What is what does boo mean from a guy?

As an AI language model, I cannot interpret the exact meaning and context of "boo" without more information. However, "boo" can be used by a guy to address his girlfriend, wife, or partner as a term of endearment. It can also be used playfully with friends or as an expression of surprise or disappointment. In general, the meaning of "boo" can vary depending on the person and the situation.