Top Definition
it is appropriate to call someone a mong biff when they have done something utterly stupid and/or idiotic.

it can involve more than one person, the person who notices the act of specialness will say "Mong" and it is open for anyone else to add "Biff"

bringing more humiliation to the person who experience the special moment
Chris walks into a lamp-post
Tori cries out "MONG..."
Greg adds "BIFF"

therefore Chris is a mong biff
by jabba dabba doodlely June 30, 2010

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