Short for Pussy-Grabbing Run.
When a man goes on a mean streak of hooking up with girls. Often spurred by a shitty break up, a spiteful/bitch ex, or getting screwed over by women in general, a successful PGR lets the bra's of the world know a bro is back, and he means biz-ness.
"Your girlfriend dumped you?"
"Yeah, fuck that man..I need a good PGR right about now"
After his girlfriend dumped him and started screwing other guys the next day, Greg went on a mad PGR. Now she's pregnant, while Greg runs train all day, all night.