look up any word, like the eiffel tower:
 
2.
When a boy cheats on his girlfriend by cuming in another girls butthole.
He gwacked in her butthole.
by tracy April 14, 2004
 
1.
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
 
3.
a combination of gay and wack
That show I just saw was gwack as hell.
by lyssafacee November 11, 2006
 
4.
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 09, 2006
 
5.
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 21, 2009