HBD... HBD... WTF does HBD mean??? Hairy Bat Death? Horrible Baby Dreams??? Hilarious Bad Drivers??? Nope, you're all wrong. It's actually Happy Birth Day. You should just buy this card to show that you know what HBD stands for. You know, to be cool. Letterpress printed A2 size and blank inside. Includes a neon red envelope, but not an urban dictionary, although that would probably be helpful.