Just another way to say "happy birthday." Used when you don't have enough time to pronounce the whole phrase. Can also be used when you don't really care if someone has a happy birthday or not, but you want to at least make the gesture of saying it.
She didn't get me a gift. She just stuck her head in my office door, yelled "Habirthay!" and kept walking.
by Airbrushy October 25, 2007