Uranium by product and gouda cheese mixed together to create the one and only gack. Gack has the ability to be a tasty afternoon snack or can also perform shit rockets. shit rockets will expel chunky poo from your bum at speeds exceeding 200 mph, it will, rip your rectum in half.
WOW! I ate gack last night! and it blew my ass in half!
by goo goo the magical elf November 10, 2010
The first retching sound a cat makes when it hacks up a hairball.
I heard Morris gack after giving himself a tongue bath.
by the_great_waldo October 21, 2009
A really nasty substance. Like ear wax, saliva, boogers etc.
"Dude! Your ear phones are full of gack!"
by PaleteroJ March 27, 2010
Crank, lower quality methamphetamine not the higher quality crystam version but the stuff that is brown some times and burns like hell. There are 2 types of gack. One eye and two eye. One eye refers to the burning pain and tearing in the eye after snorting. Two eye gack makes both eyes burn and water from snorting it in one nostril.
"I did some gack last week and I still feel like shit!"
by PharmaPharmer December 30, 2004
To discharge some kind of fluid from the mouth, either phlegm, mucus or vomit.
I had a coughing fit and gacked out a lunger the size of my hand.
by amno February 13, 2003
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!
by woodfella February 14, 2009