a person who has grown significant fat rolls around their middle/waist/arms, any part of the body really and who feel the need to sit there with clothes that are far too tight and lean over showing their stretch marks to the world
a saggy maggy is someone who has ate too many burgers or "all the pies" as they say in wigan
An ill-fitting condom, specifically those of the Trojan Magnum variety; or a man wearing a clearly over sized condom.
Gabbi: "So how'd your date go last night? did you give him some?"
Annie: "Dinner was ok but when we got home he pulled out a magnum...."
Gabbi: "What's wrong with that?"
Annie: "He is to small for all of that!"
Gabbi: "Just say NO to Saggy Maggys!"