The act of holding your straw like a knife and then shanking your buddy's large McDonald's cup on the side in an attempt to make a huge mess. This only works with the large cup since it's the only one made out of styrofoam .
Leo (thinking): I should McShank Hans just because i'm bored....
*Leo then McShanks Hans' large cup*
Hans: Hey man! WTF! you ruined my cup and made a mess!!!
Leo: How You Like Me NOW!!!