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To gain weight through extra fat "marbling". Term derived from cattle industry practice of fattening animals prior processing into food. This fat, streaked through the meat, provides extra flavor and richness.
Observing your friend downing a large bowl of ice cream, you say: "Marble up dude!".

Exclaiming to your ultra-fit skinny buddy: "You need to marble up!".
by D. Gilbert June 21, 2007
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