When a man masturbates underneath a blanket, and it appears as if he is punching the blanket due to the rapid up-and-down movement of his hand. This can also be used as a joke by a guy who wants to appear as if he is masturbating, however when he is asked what he's doing, he simply says, "I'm punching the blanket."

When you eat dirt for the first time and leave your family to build a shack in the woods