Becomming more popular than EYL (end your life) and KYS (kill yourself)
Guy 1: "Dude, you're fucking dumb EYL"
Guy 2: "Ohh look over there, a gun SYS"
Guy 1: "Ok, fine I will"
Short for See You Soon.
Guy: I'll be right there
This has quite a few meanings.
1: (My Favourite) SHUT YOUR SHIT!
2: Shoot yourself.
3: Slap yourself.
4: See you soon.
Example for the 1st meaning.
Tim: Dude omg i love cod man.. it's like the best game everr!!! i pr0 snipez omg!!
Simon: Dude, SYS.
Slap Your Self