shell suit 
noun British
A casual outfit consisting of a loose jacket and trousers with elasticated waist, having a soft lining and a shiny polyester outer shell.That, and the fact that almost everyone in Horden wears a shell suit or football shirt and trainers at all times, persuaded him to try the fitness industry....
- He is of course pure chav already although the thought of him in trackies or a shell suit is not a pleasing image.
- But with the advent of softer fabrics and the dreaded shell suit, fashions changed and the tweed producers fell on hard times.