Ok, summary time. The word or acronym M.O.S. can have several meanings:

1. Member of the Opposite Sex
2. Mutual Oral Sex (see 69)
3. Make out session
4. "Mom over shoulder", a warning in chatrooms or IMs
5. Ministry of Sound, a nightclub in London UK
6. A short form for mos def, which is a short form for "most definitely".
7. Military Occupational Specialty (US Army)

M.O.S. can also be an abbreviation of a shitload of other terms that are mos def not used in slang. Including Metal-Oxide Semiconductor, Made of Steel, Marine Observation Satellite, Medical Outcomes Study, Member of Service, Mode Of Shipment etc.
Err... recently 2 London grrlz on aim:

A: "So tell me what happened after the party at MoS last night!"
B: "Ok, I was just about to leave when I met this really handsome MOS.
He told me his MOS is Infantryman in the US Army. Guys in uniform just turn me on!"
A: "Sweet, and then? Did you make out with him?"
B: "Yes! We had a good mos in the club and then he asked me if I wanted to come to his place, I said 'mos!'"
A: "Really, so did you...?"
B: "Yeah, when we got there, we started to have some real good MOS..."
A: "Wait, MOS!"
B: "Ok, ttyl ;)"
by 007 Bond November 20, 2006
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a bastardization of mos def meaning "I concur" or "Affirmative"
"man, this food they're serving blows"
"mos."

-or-
"are you going to join the riots tonight?"
"mos."
by Mos Def January 21, 2004
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It is like dimsim but only a thousand times tastier it is dipped in delicious sauce and eaten. Main momo's are chicken and buff.
chicken Mo mosare so nice!
by nepalyz_urbdictinary June 19, 2006
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