Definition 1 of 2
Smacking the forehead with an open palm. Done out of exasperation or annoyance.
When Swami came home and told granny that he had lost his slate, she beat her forehead and said, "Aiyyo! What a careless fellow! If your head was not attached to your body, I'm sure you would lose that also!"
Added 2011-09-08 by Bimawala