What does barmy mean in British slang?

"Barmy" in British slang means crazy, foolish, or eccentric. It's a very informal term, often used humorously.

Here are some examples:

* "He's gone completely barmy!" (He's acting crazy.)

* "That's a barmy idea!" (That's a foolish idea.)

* "She's a bit barmy, but in a good way." (She's a bit eccentric, but in a charming way.)

It's important to note that "barmy" is generally considered mildly offensive and should be used with caution, especially when addressing someone directly.