Definitions by L8Nighter

gack 

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!"

gack by L8Nighter March 17, 2011