Similar to the sex act referred to as the "Cosby Sweater", the "Dirty Pancho" is a sex act performed when one partner eats Taco Bell or another kind of Mexican food and shits on the receiving partner's chest/stomach area for the arousal of one or both parties.
"Dude, Maria ate some Chipotle and a few hours later gave me the best Dirty Pancho I've ever had."

"Luci gave me my first Dirty Pancho last night and I came so hard."
by alexinwunderland February 17, 2014
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