What is what does it mean when a guy says chill out?

When a guy says "chill out", it usually means that the person is being too intense or overreacting to a situation. It is a request for the person to calm down, relax, and not take things too seriously. It can also be used as a way to de-escalate a tense situation or to diffuse an argument. However, it is important to understand that the phrase can be interpreted differently depending on the context and relationship between the individuals involved.