look up any word, like cunt:
 
2.
SDI
Acronym for "sucks, doesn't it?"
Monday-
You: What'd you get on your test?
Me: I failed :(
You: Hahaha. Good job, fuckhead.

Friday-
You: Dude, I totally just failed my test in bio :(
Me: SDI. XD
by Margo Roth Spiegelman II April 14, 2009
 
1.
sdi
"Stratigic Defense Instatute". It could be some kind of super secret military organisation so secret that nobody knows the slightest damned thing about it. Or the previous description simply matches the wet dream of some guy, when in reality it's just the "company" name of some guy who made an unlicenced Star Trek board game.

Synonym: 'pathetic'.
"I am not the computer wiz! Dr.'s Bob and Geodude have that responcability. I've told you all before, It's not my yob, man!"
by Lord of the Farce April 07, 2004
 
3.
SDI
a bunch of nerd, left out, people located at makati, philippines.
they are movie subtitlist who works from 7:00 am to 4:00 am the next day. they are devided into two groups- the EU team are the ones who are making english master templates for the europian movie translators and the LA team is the one producing dvd file for SDI LA...
don't ask about the salary... it sucks!
-i have some new dormmates, dude.
-are they cool?
-naah, they are SDI.

-our boss loves the new guy.
-why?
-coz he works hard, he's SDI.

by sker lao May 04, 2007
 
4.
SDI
imaginary instatute made up by a 1337 master of "tai qwan doe" who is richer than god and lives in his parents' basement.

either that or a really sad 50 year old
the explosion is really a ring, not a circle!
by General Zod April 07, 2004
 
5.
1.Statigic Defence Initative, Also known as "star wars"a plan to "Knock out" nuclear missiles in flight before they reach the U.S.A In the event of a nuclear war. 2.A song by Loudness; the opening track on the 1987 album, "Hurricane Eyes" the song's lyrics deal with the issue of nuclear war
In the 1980s a defence plan (known as "star-wars") was developed by the the president to protect the U.S.A. from a nuclear attack -this was known as S.D.I.
by koi-boy March 14, 2010