A mentally competent, fully developed person capable of only the most basic human functions, most notably eating, fighting and/or fornicating.

The word is derived from the word "pound" describing in basic slang terms the act of punching or having sexual intercourse, and the word "box" which implies that the person's brain is an empty box.
Sure, she's hot. But she's also a giant poundbox.
by Thesaurius Moduris January 14, 2014
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