look up any word, like the eiffel tower:
 
2.
Shit In, Shit Out: If you're putting shit data into an experiment, you're going to get shit data out.
Your results are bubkes, what did you expect? SISO!
by Mike Schroll March 13, 2010
 
1.
a retard or to be retarded. Its name originates from a school called Sisobel for mentally challenged people.
1. George is being siso. (George is being retarded)
2. George is a siso. (George is a retard)
by Jimmy Cracked Corn April 11, 2008
 
3.
Siso stands for "spicy in, spicy out". A phrase to help us remember that although spicy things taste good, they may also burn the hell out of your a-hole on the way out.
Person 1: What kind of wings should we get? Inferno?

Person 2: Siso, bro. You don't want an ass like a Japanese flag, do you?

Person 1: Good point, let's get teriyaki.
by juicien June 12, 2011