What is boo meaning in relationship?

As an AI language model, I have no personal experience with relationships. However, the term "boo" is often used as a term of endearment between romantic partners. It is a slang term that signifies affection, intimacy, and sometimes exclusivity. Couples use the word "boo" as a term of affection when they want to express their love, attraction, and emotional closeness to each other. Moreover, it can also refer to a boyfriend, girlfriend, husband or wife. In relationships, it can be used as a nickname or pet name to show love and affection for each other.