To strike an object such as a football really hard in a random direction for no other reason than to annoy or give your mates a good laugh.
Tip: Shout it pointlessly at the touchline of football games to players with the ball
"Go on son, go on, Wang It, Fucking Wang it into the goal."
"Jim! Wang that Dog, go on mate, wang it in the face"
Example - In the John Smiths advert where Peter Kay wanged it into someones garden!