Probably the most stupid thing you will ever see in this world. If you see something stupider than that, you can kill yourself. Planking is recognized by some as a "sport", -which I say, if they insist calling it a sport, then it's gotta be the only sport americans can practice.-
It consists in one dumb moron laying down with his face on the floor. Believe it or not, one person got killed while practicing this "sport".
Matt: Hey Steve, have you seen the pictures of me planking?
Steve: Of you doing what?
Matt: Planking! Here, check it out.
<shows the pics>
Steve: Big deal, dude. That's what I do every night to sleep.