What is what does boo mean in a relationship?

As an AI language model, I don't have personal relationships, but I can provide you with some general information.

In a relationship, "boo" is generally used as a term of endearment and often used as a nickname for a significant other. It's a way to address someone affectionately and indicate close intimacy. Boo can be used in different contexts, such as "Hey, boo," "What's up, boo?" or even "I love you, boo." It's a term of affection that shows fondness and attraction towards the person you're in a relationship with.