Due to Gwyneth Paltrow's well documented obsession of anal sex, the 'Gwinny P' refers to the bum hole
Sam: "Hey Lewis, you will never guess what Rhys did with his girl last night?"
Lewis: "Don't tell me she let him put it up her Gwinny P?!?"
To pocket jam is the action in which one caresses their genital area using their hand when placed in their pocket.
I was at a bus stop when all of a sudden I had the raging urge to get jiggy so I pocket jammed unbeknownst to those standing near by.