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1.
MPE
Marinate, Perculate, Evacuate.

The 3 steps to taking a shit.
First you Marinate...that's when you feel a little something in your stomach, but you know you aren't ready yet. Second you Percolate, that is when you hear "percolation" in your stomach...almost like something in boiling in there. Last but not least, Evacuation....that is when the feces exits your body, the complete process of this is known as MPE.
by Mutha F'r Jones August 30, 2011
 
2.
mpe
A.) Miles per eatage; B.) My point exactly
A.) Man, slow down!!! We're in public and you're eating at 90mpe! B.) Jeff: How did I get in trouble for not snitching? Chris: Usually your parents tell you NOT to be a tattle-tell! Jeff: MPE!!!
by Jaicii Tillsen August 06, 2008