What it means
What a bomber is depends on where you are. In the UK, Ireland, and Australia it's an older but still kicking term for a good-looking woman or man, a compliment that's stood the test of time. In North America it's more about the jacket, like a bomber jacket, and in some places it's a type of large marijuana cigarette. The context tells you which one's in play.
Usage examples
"Did you see that bomber at the pub last night? Absolutely stunning."
"He's a proper bomber, that lad, all the girls chase him."
"She walked in looking like a total bomber and the whole room turned."
