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Methamphetamine (crank, speed). Describes the gag reflex triggered by the extreme burning sensation of the nasal passages when the drug is snorted, and the very bitter taste as it drains down the back of the throat.
The character 'Pooh-Bear' in the movie "The Salton Sea" had to have his nose surgically removed because he snorted too much gack.
by Anonymous July 13, 2003
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Any amount of useless or unwanted stuff (usually regarding possesions)
I've got too much damn gack in my attic. Guess I'll throw something on ebay.
by mudpup April 05, 2006
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To borrow or steal internet content from another user.
I gacked this meme from lamebrain426.
by florimell August 09, 2003
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1.A term used for the Drug Crystal Meth Amphetamine

2A some what derogatory name for person under the influence of crystal meth.
1. "They just smoked a fat bowl of gack."

or Thats some killer Gack!"
2. "That guy is a total effin gack." or "Quit being such a gack, your going to get us busted!" or "Never bring that gack over to my house again!"
by L8Nighter March 02, 2011
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The sound made by an individual who is in the process of sucking dick. Typically a gagging sound made from the throat.
Brenda gacks on that niggas dick because she has a terrible gag reflex.

That chicken head is always gacking choad in the park.
by Catsleeze September 23, 2013
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Gack is not a word but an emotion of pain and joy. And also a good word to say after dabbing on the haters
by Joebo kenysville February 19, 2019
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