gack 

The slimy substance (usually green) that was dumped on people in earyl Nickelodeon tv shows

"Thats the incorrect answer so you get drenched by a bucket of gack"

gack by Cane May 1, 2005

Gack 

A really nasty substance. Like ear wax, saliva, boogers etc.

"Dude! Your ear phones are full of gack!"

Gack by PaleteroJ March 27, 2010

gack 

Similar to a circus "geek", a "gack" is a circus performer who sucks farts out of chickens.

It was amazing how the circus gack was able to withdraw flatulence from the hens and roosters.

gack by J.J.W. November 22, 2004

Gack 

A noun used to insult anyone that looks, talks, or acts like a dork.

OMG, don't let Stewart come with us tonight, that dude is a fucking gack.

Gack by Richard Huang November 6, 2004

Gack 

A Gack is any item (other than a bottle opener) which is used to open a beer bottle. This applies only to bottles filled with beer. Soda, juice, de-alcoholized beer etc. do not apply. It must also not be a screw-off bottle. Due to the skill involved, a person who is rather adept at using various items to open a beer is referred to as a Gacksmith.

My buddy Todd is a real Gacksmith. He can make a Gack out of anything!

Gack by woodfella February 14, 2009

gack 

The browny black substance found inside a firing tube after a big mix has been smoked through it,It smells terrible and stains lips, clothing and fingers

John smoked a massive bong and got serious gack on his lip.
The bong was covered in gack

gack by erbivore198999 February 25, 2009

gack 

Term used by live and recording soundmen to describe old and broken audio equipment

Take that out of the rack and put it with the rest of the gack in corner

gack by R Caron December 4, 2003