oS stands for Old School. 'Tis an abbreviation for oS.

The lowercase-then-uppercase type is a way of making it look cooler. "oS" originated from Nitto 1320 Challenge, where we painted oS on our cars while on the team OldSchoolRacing, and even use oS on our cars to show that we've been playing for a long time and say it in chats across the web to this day. A note, oS should not be said in real life, you just say "Old School".
Ice Cube is Old School.
Ice Cube is oS.

The oS's are what makes OldSchoolRacing the best.
by protectmeaura December 11, 2006
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Two SYTYCD fans chatting: Saw it on a Pops Poll on OS.
by L.Skywalker March 10, 2009
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This is an abbreviation used exclusively for games in the Halo series. It stands for OverShield.
p1: wtf? how didn't you die?

p2: I picked up an OS
by DrΓΌd August 31, 2008
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slang terminology for OVARIES. the feminine version of the term "balls".
by stretchmarx June 21, 2007
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A nicer way of calling someone a 'Hoe'
Ayye manggg, you see those O's over there? I heard they give good head!
by doodmamas<3 December 09, 2009
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Slang word for a power up in the popular game Halo 2 means Overshield. Gives you 2 extra layers of shield
"Pick up the OS you wont die!"
by Mex4life1992 November 11, 2006
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'The O's' is the nickname for East London footie club, Leyton Orient. Also for their rather nondescript hooligan crew.
by Ned September 20, 2003
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