A comment intended to display knowledge of a subject which instead exposes the ignorance of the person who made it. Derived from a scene in "The 40 Year Old Virgin" when the main character's virginity is obvious due to his story about a woman's breast feeling like a bag of sand.
Sarah Palin's claim that she regularly reads every newspaper ever printed was a "bag of sand" moment for the governor.
by omgboomer July 01, 2009