PMBM 

Having a bad case of the shits in the night time. PM=nightime BM=bowel movements, therefore PMBM=nightime bowel movement.

Dan-"Hey dude, wanna go out to a club and pick up some babes tonight?"

Jeremy-"Nah dude, I'm feeling a bad case of the PMBM coming on"

Dan-"Gross"

PMBM by peter Stefanos September 23, 2006

PMBM 

noun: a bowel movement occurring during the second half of the day.

Queen of England: Sir, do you take thy daily deuce in the morning, as I do?

Factory Stiff: No, your Highness. Ever since I got on third shift I've been rocking a PMBM.

PMBM by honkus mcduck May 14, 2009

pm bm 

A bowel movement that takes place in between 1:00pm and 12:00pm.

That pm bm destroyed my toilet dude.

pm bm by brainpowerintheshower6969 June 21, 2010