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1.
Used to explain when something you eat is so gigantic all you can do is grunt and chew.

Slang: can also be used to describe the male genitalia.
Example 1
Guy 1: Dude why are you grunting so much?
Guy 2: because this burger is just so Gigruntic.

Example 2
Girl: My new boyfriends dick is so Gigruntic I can barely fit it in my mouth.
by TheInvader July 10, 2011