1. A Person: This is the most common meaning. It's used to refer to a person, often in a general sense.
* "There's a right good laugh at the pub tonight, I'm going with some mates."
* "Did you see that a on the telly? They were acting like a right idiot."
2. An Article: This refers to an item, often something specific.
* "Did you bring a?" (meaning: did you bring something, like a drink or a snack)
* "Have you seen a about this?" (meaning: have you seen something about this topic)
3. "A" as a filler word: Like "um" in American slang, "a" can be used as a filler word to buy time while thinking.
* "Right, so, a... the thing is, I need your help with this."
4. "A" as part of slang phrases: It can be part of slang phrases, which might be more specific to a region or social group.
* "Have a good one!" (meaning: have a good day/time)
* "Go and have a gander!" (meaning: go and have a look)
It's important to understand the context to decipher the meaning of "a" in British slang.
Note: These are just some examples and there may be other meanings depending on the specific situation.