These are the sort of knickers that are featured in Bridget Jones' Diary.
"It was so embarrassing. My trousers fell down and the whole world was staring at my granny pants."
usually baggy and old, the kind you wear for comfort and not for looks.
mostly grey as a result of bad washing, usually stretched with age and often seriously lacking elastic.
pants that i would be devastated to be caught wearing in the throws of fondling.