Si 

Having a sign language rap battle.

Tommy couldn't hear the shit that Warren was signing about him.

Si by will bitten December 21, 2016

SI 

Abbr. for 'stupid idiot'

As in Football Factory from 2004:
"Jog on, you si!"

SI by Nige Menzel June 11, 2007

Si 

Yes

“Si”

Si by TwistyNoodles July 27, 2020

SI 

Abbr. for "self-injury," also known as self-mutilation. Most common form is cutting, but may also include burning, bruising, skin-picking (excoriation), and other behaviors. There is no single cause for SI. SI is most common in women and tends to persist for years.

As a result of overwhelming anxiety, she turned to SI as a coping mechanism.

SI by rieux November 27, 2003

SI 

stands for self-injury. Aka cutting, burning, etc. for emotional distress reasons

Person 1- Did you SI today?

Person 2- I haven't hurt myself on purpose in like a week.

SI by Injuried November 8, 2010

si 

Short for "System International." Also known as the Metric System.

The SI system makes more sense than the English system. It should be officially adopted by the US, but we Americans are too lazy for change.

si by BlastMaster June 12, 2003

Si 

An awesome boy that is kind, nice, derpy, hilarious and clumsy and is a wonderful bestfriend.

Is that Si?!

Si by kjj-123 December 30, 2012