Magazines that contain images of the female species in various states of undress.
In some cases these images include red jacket shots
"Oh bollocks Dad, have you been borrowing my jazz mags again"
(Eng.) Slang term for pornographic literature.
"Gross, you got my jazz mag all wet."
A specialist gentleman's publication often enjoyed lying down with the curtains closed.
Father: "There's a lot of banging going on upstairs, where's young Steven?"
Mother: "He's in his room, reading"
Father: "Hm, he's probably looking at a Jazz Mag"
Mother: "Good gracious no, he's not that kind of boy. He's probably just exercising, and he's never liked Jazz music"
Aww but Mrs my mum found my Jazz mags underneath my pillow last night!