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.

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?!

by kjj-123 December 30, 2012

si

Its a model of faster model of the Honda Civic, meaning "Sport Injection"

My civic DX got spanked by that Si hatck.
or
Im bout to get me some Si rimz dawg.

by Tsugaru November 26, 2003

Si

1. Spanish for "yes".

2. Abbreviation for "suck it!"

3. Abreviatiin for "self injury"

Wy don't u si!

by Bojojo July 5, 2011

SI

1. Spanish for "yes."
2. Misspelling of "is."

1. "I suck." "Si."
2. "NO YUO FAGOT A COMPUTAR SI NOT A HAT!"

by Dj gs68 September 22, 2003

SI

self-injury

I haven't SI'd in two weeks.

by Anonymous Ex-cutter June 21, 2003

SIS

Snickering in Silence
new for LOL because it applies much more than LOL when texting/typing and trying to be quite

While texting in class i received a message with a prime time to say "thats what she said" and/or "reminds me of my saturday night" or even "I get that all the time" so I sis'd vs lol'ing

"idk what happened it just went everywhere after i touched it"
sis
"reminds me of my saturday night"

by kevin "k-bone" December 25, 2009