Acronym for Sexually Educated Girl. The type of girl that has received a significant sexual education so that she avoid's all measures to avoid getting pregnant or catching an STD.
Dude 1: So shall we do it,

SEG: Yes, Do you have a condom? First I need to see the expiry date on your condom. Is it a Trojan or Durex, or Store brand? Where have you stored you condom, in dry warm conditions? Do you have lube? Is it water based or oil based? I think just to be sure, I better give you a blowjob with two condoms on.

Dude: Dayuuum girl, you a SEG!
by TheMadFelcher April 18, 2010
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Describing a fat persons protruding gut.
‘Wow look at the Seg on the bloke

‘That lady has a massive Seg’
by Truv January 13, 2021
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Sex act. Both participants start in a standing position facing each other. They both raise their arms above their heads in a full stretch. One penetrates the other and they both lean backward forming a Y shape - a self balancing "segway" like structure.
John snapped his penis off last night in a freak segging accident.
by Lyle Plapp Phd. March 21, 2019
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Short for segment, segamatron, seggie, segmeena and segatron (a variation on segamatron), a Seg is a creature of very small stature, likened to a hobbit, of JRR Tolkien fame. They feed on blackcurrant cordial and baked potatoes, and move around in a shuffling manner. They are extremely rare and have often had other animals, such as kia, the wife of the famous willow mistaken for them.
Fo shizzle segamatron, you is lookin supa-fly in eric 2day.
by Pete November 17, 2003
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Lame self-created nickname by a faggoty 12 year old and clung to throughout adulthood, as if it is interesting or exotic. Possibly copied from an obscure Star Track character or a monster from the early 90's Power Rangers.
Let's go to Segs! We can play video games and get fucked up like the 14 year olds we will always be!
by coo coo bird April 25, 2009
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Seg = 539. 539 is 1337 in hexadecimal form. Too many people were found to be using 1337, therefor the truely 1337 have turned towards their base 16 saviour, hexadecimal numbers!
Seg, or 539, can be used instead of the word 'Sex', as well as meaning 1337. eg...

-I'm so 539sy (I'm so sexy)
-OMG 539 (Oh My God, 1337)
-539z0r HaxXz0r (1337 hacker)
by An@rchy May 25, 2004
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