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2.
A fattening food that makes you happy when you eat it.
or
Food that makes fat people euphorically happy.
Potato chips are my fatnip.
by Gab & Christian June 16, 2009
 
1.
Some unlucky guy who is considered the catnip for fat chicks. Obesity chases him as if he were chocolate cheesecake.
Those bitches smelled fatnip the second that they walked in and plowed right through us to get to my poor boy Steve.
by HFP March 16, 2007