When you have several instant messenger windows open and you accidentally type something into one of them that was meant to go to another person. Usually something that can get you in trouble if it goes to the wrong recipient. Similar to a brain fart.
Oh no, I just totally windowfarted and sent the following message to my boss instead of my friend.

Message - "Did you hear that he smoked a joint in the hallway outside the office yesterday?"
by PixieBug August 22, 2008
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