a large handbag that can be carried by a strap looped over the shoulder

a very large purse that is full of so much stuff you have to carry it on your shoulder because it's so heavy

any bag with a shoulder strap.

Any handbag that has a long strap and is intended to be worn over the shoulder. Shoulder bags are popular when moving in crowded public places as the strap can be worn across the body to thwart purse-snatchers.

handbag looped over the shoulder by a strap