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1 definition by Sid Dslaci

In a state of abject panic; acting out frantically and aimlessly. Derived from the image of someone running around waving their arms wildly, ricocheting off walls, and yelling gibberish at the top of their lungs, all while wearing underpants on their head.
"If space aliens ever invade, I just know I'll go totally underwearhead."
by Sid Dslaci June 04, 2006