It means that you have a hot sister and when you look at her you get a stiffy. IE: Stiffy Over Sister
by Bini November 26, 2004
Get the SOSmug. by dmack23 April 1, 2010
Get the so badass!mug. Commonly used irreverent phrase when spoofing popular comedian Jerry Seinfeld from the show Seinfeld. Other common phrases include "whats the dealllll?" and "who arrrrrrre these people?" While first made popular by fellow comedians such as Gilbert Gottfried, it is now popular for ordinary fans/detractors of Seinfeld to use this phrases as an imitation or parody.
by JoeROE1234 September 20, 2010
Get the so heymug. by Avi Orlow June 17, 2007
Get the That is so Plutomug. by lwlwlw October 5, 2008
Get the that's so sketchmug. 
