On the show Torchwood, the relationship between the characters Gwen Cooper and Captain Jack Harkness is known as Gwack(in the style of 'ship names like Spuffy).

This relationship is terrible. seriously, it's so badly conceived. It just doesn't work. Therefore gwack can be used as to describe anything terrible.

It's also a great onomatopoeia for vomiting. Honestly - Gwaaaaaaaaaaaaack. Which Gwack makes people want to do.
"What a pile of gwack"

"Seriously, I'm going to gwack"

"Gwack make me want to gwack"
by Cuilean March 30, 2008
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When a boy cheats on his girlfriend by cuming in another girls butthole.
He gwacked in her butthole.
by tracy April 15, 2004
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That show I just saw was gwack as hell.
by lyssafacee November 11, 2006
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A middle name given to a guy named Kevin, from a guy named Justin.
Kevin Gwack Nguyen has a stupid crippled foot, and he walks slow. But, he`s cool and we love him.
by amandarose September 10, 2006
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A pairing from the show Torchwood, with the characters Gwen Cooper and Captain Jack Harkness.
It is one of the canon pairing in the series alongside Janto and Towen. (I anto Jone x Jack Harkness & Owen Harper and Toshiko Sato)
Many fans ship this pairing, but since Janto has gone canon, many have supported Janto instead.
Gwack is a canon pairing from Torchwood.

by AnetteVee March 22, 2009
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gwack is another name for giving head better known as a BJ aka Blow Job

this name is taken from the sound you make when you deep throat and your gag reflexes go off "gwaaaaaaaaacckkk"
"Gwack 2.0 " is giving/recieveing head by/from a sexual partner
I was at this party last week and this hun offered me "Gwack", she went down on me hard
My girlfriend prefers to swallow when she gives me "Gwack"
by Micca Cummings June 10, 2023
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