1. an orgasm, a sexual climax

2. opium
Once I reach the big O, there is no turning back.
by The Return Of Light Joker November 5, 2007
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a giant robot in the anime big O
guy:*looks at watch* BIG O! *robot appears*
by O_oo_O July 17, 2003
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one who is large, cheerful, and especially O-ish in nature
"Big O has got to be the coolest kid in the world.....next to Kearney"
by Big O April 24, 2003
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u do the big O today? u're all funny

many chinx were doin the big O back in the 19th century.
by big O November 26, 2003
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1. An intense Orgasm let off by a female that squirts more than a foot away.
2. A Nice Oz of weed
3. The face she makes when she's riding a big black dick.
1. I got Jen to do the big o when i was eating her out last night, she almost shot me in the eye.

2. Hook me up with a Big o, i got a vaca from work- gonna smoke my brains out.

3. She must've liked it cuz she had a big o on her face the way she was moanin and screamin.
by Speciial Kay April 23, 2009
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