ALT + F4 

An unoriginal old prank that nobody falls for anymore, (except the 10 years olds)

10 Year old has joined the game.
10 Year old: Hey how do you run fast?
xxmLGpro69x: Press and hold ALT + F4
10 Year old has left the game.

ALT + F4 by this is really long name February 5, 2016

Alt + F4 

Keyboard command to exit out whatever it is you are in.

Press Alt + F4 right now to close out Urban Dictionary.

Alt + F4 by flclimax1 February 6, 2008

Alt + F4 

The best way to save any important document

Just try it. Alt + F4

Alt + F4 by kohlmanfrack April 20, 2010

Alt + F4 

shortcut key for nearly all Windows Operating Systems to Close the active window or application.
Also used as an insulting tool by the 1337 or l33t people to have a bad/angry gamers, aka noob, to trick them to quit the game.

friend: dude, how do I quit this?
me: hold 'Alt' and press the 'F4' key at the top of the keyboard.

also
l33t: to fix the lag, hold Alt and press F4
<random noobs log out>
l33t: sweet, less lag...works all the time.

Alt + F4 by Edward Evil, CEO of Evil INC November 16, 2004

Alt + F4 

Used in online games to 'pwn'/scam 'nobbies' due to the fact that this command closes your current open window.

l337: To duplicate money/items drop them on the ground and press alt+f4

Nub: OK!

(nub leaves game)

l337: haha, j00 got pwnt

Alt + F4 by JimE Ray January 24, 2005

Alt + F4 

if u want to achieve something in your life press that button

none

Alt + F4 by Arnold the governator October 20, 2003

Alt + F4 

Often used to discourage n00bs, this is often said while playing a game or talking in a chat room. Usually results in never seeing the n00b again.

n00b: I JUST WON A GAME!
Player: Press Alt + F4 please.
<n00b> has left the game.

Alt + F4 by RyaN February 19, 2003