A Graphical User Interface. The addition of GUI's to most modern operating systems has revolutionised the populous' ability access pornographic material, and contributed greatly to the happiness of the single geek/male population.
Stands for "Genius Under the Influence". It is a term used for individuals who come up with fantastic ideas when abusing some kind of substance, or for those students who actually do quality schoolwork while completely fucked up.
Student # 1: "I can't believe I got an 'A' on that paper. I was so high when I did it I couldn't even remember what I wrote about."
Student # 2: "WTF. You should totally be charged with a GUI."
pronounced as Jooey: Sometimes you just cant decide wether you'd rather play some good old fashioned COD or get a nice blow from your girlfriend. Why not settle for both. This is where the GUI come in... Gaming under the influence. Now you can play with both sticks at the same time.
Tommy was ignoring his girlfriend Laura, being he was in the middle of level 27 on Nazi Zombies. In order to resolve this conflict Laura proposed a GUI, which allowed him to keep his tip wet and destroy some zombies all at the same time.
Bill: GUI, GUI, GUI, yea, shove that loaf of bread in my asshole more Steve
Steve: Ok Bill. Your turn.
Bill: alrighty:
Steve: GUI GUI GU- OUCH! That really hurt bill