Someone who is useless at life. They usually screw everything up without even trying.
Dave: "what happens when If I touch this?"
Person 1: "it doesn't matter, just don't do it"
Dave: "oh god, I broke it"
Person 1: "I just told you not to touch it...Fuck up!"
1. Screwsomething up, completely fail at something
2. Shortened way to say "shut the fuck up"
3. (Australia) Something you say to initiate a fight with some cunt. Basically "stand/get the fuck up".