To be so high, from smoking marijuana, that you cannot move or speak. Commonly used by stoners who are bored with the commom slang. Associated with the stillness of a distant mountain goat standing peacefully.
Phil "why didnt you come by last night, we had fun."

Eric "Dude, I didnt feel like doing anything last night, I was high as a goat."
by casanova8231 November 30, 2010
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