What does idiom mean his

You're likely asking about the idiom "his". However, "his" isn't an idiom by itself. It's a possessive pronoun, meaning "belonging to him".

To understand what you're looking for, I need more context. Could you please provide the full phrase or sentence where you encountered "his"?

For example:

* "He's got his head in the clouds." This is an idiom meaning "He's not paying attention to reality."

* "His bark is worse than his bite." This idiom means "He seems aggressive, but he's actually harmless."

Once you provide the full phrase, I can help you understand the idiom it's part of.