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Acronym for Post Ejaculatory Urinary Misfire. After ejaculating (either through masturbation or copulation), if all of the semen is not expelled, some may remain in the urethra, developing a slightly more solid phase.

As the male attempts to urinate later (often the next morning), the urine may spray in multiple directions as a result of the blockage.
Man, I had to clean up my bathroom for 30 minutes this morning because I had a killer PEUM.
by Eli Kennedy July 18, 2006
It stands for Post Ejaculatory Urninary Malfunction. After a male ejaculate and then tries to urniate there are always multiple streams and strange angles.
Sorry, honey. I pissed on the blinds again. Damn peum.
by Tad Allen September 13, 2004