The act of ejaculating, so many times during a period of time such that you do not feel the desire to ejaculate anymore.
MARY: Hey, John, I'm back for reading week, let's have sex
JOHN: Naw, sorry babe, I've been using my right hand for the past hour, and I'm all jacked out.
To lose through the sheer dumb luck of an unlikely event which would normally be crap.
Guy: I top 8'd recently at a children's card game event but got janked out by a kidrunning Horn of the Unicorn Control... Suxors. Should have run Monarchs.