Select the most appropriate meaning of the given idiom.

In your birthday suit

Not wearing any clothes

The most appropriate meaning of the idiom "in your birthday suit" is not wearing any clothes.

The phrase comes from the idea that when a baby is born, it is not wearing any clothes. So, being "in your birthday suit" means being naked.

The idiom is often used in a humorous way, but it can also be used in a more serious way. For example, you might say that someone is "in their birthday suit" if they are sunbathing or swimming naked. Or, you might say that someone is "in their birthday suit" if they are caught in a compromising position.

The other possible meanings of the idiom "in your birthday suit" are not as common. A "suit which covers one's entire body" is called a full body suit. "Birthday celebrations" are the events that take place on someone's birthday. And a "suit which is designed for only birthday functions" does not exist.