1.) A South African English expression roughly equivalent to the American "yech" and the Afrikaans expression "sies".

2.) An American term of endearment for a sister, now also used in other countries.
1.) Sis, man, you stink!

2.) Hey, sis, hey bro, how's Ma doin'?
by Xaviana December 1, 2003
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a genderless term much like "bro" or "dude"

you don’t have to be BFFS. You don’t really even have to know them. If she seem chill. then SISSSSSS is what they should be called!
JACK: *texts Jill*

“ SIS! You’ll never believe what popped up on Greg’s phone!!”

Jill: “Girl, SPILL!”

Jack: “Some HOE’S NAME! Do you think he is cheating on me?!”

Jill: “ SIS! YES! Leave his ass!”

****you can also use it in less dramatic scenarios****
by URB@NL3GEND March 5, 2020
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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 13, 2003
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An awesome boy that is kind, nice, derpy, hilarious and clumsy and is a wonderful bestfriend.
Is that Si?!
by kjj-123 December 30, 2013
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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 27, 2003
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1. Spanish for "yes".

2. Abbreviation for "suck it!"

3. Abreviatiin for "self injury"
Wy don't u si!
by Bojojo July 4, 2011
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