1) Acronym used for the phrase "shut the fuck up" for efficiency reasons.

1.) Save The Freaking Unicorns
2.) Say, Thanks For Understanding
3.) Short Term Follow Up
4.) Special Task Force Union
5.) Stop Talking Find Username
6.) Slippery Teflon From Utah
7.) Stinky Telnet Fell Under
8.) Special Transitory Food Units
9.) Stealing Turkeys From Uncle
10.) Superior Tactical Fragging Unit
11.) Silence That Followed Us
12.) South Texas Farming University
13.) Southern Tenant Farmers Union
14.) Scrawny Two Faced Underling
15.) Samurai Training Finished Unsuccessfully
16.) Show Them Fury Unleashed

Or the most common definition:
17.) Shut The Fuck Up
The common response to the previous 16 definitions.

"Shut the Fuck Up"
To the extent of being universally known, consistently used online, both on multiplayer games and messege boards.

Practiced in anger or irritation, to get someone to remain quiet.

With or without "Bitch", "Woman" or any demeaning and vulgar slang to show pwnership.

An abbreviated form of:

Shut The Fuck Up

Often used in the popular internet comic "Little Gamers" and on internet message board and chat rooms across the nation.

A way of saying "shut the fuck up", instead of actually typing it. Has less meaning than actually typing "shut the fuck up", and is often said by people that are losing an argument or can't think of a comeback.

Southern Tenant Farmers' Union (STFU): Large labor union, formed in Arkansas in 1934, which lobbied the federal government for better New Deal reforms. Dissolved in 1960. Commonly causes mirth among US History students who are aware of the acronym's double meaning.