1an outer garment extending either to the waist or the hips, typically having sleeves and a fastening down the front: [as modifier]:he put his hand in his jacket pocket
2an outer covering, especially one placed round a tank or pipe to insulate it.
the dust jacket of a book.
a record sleeve.
3British the skin of a potato:potatoes cooked in their jackets
informal a jacket potato.
4US a folder or envelope containing an official document or file.
5a steel frame fixed to the seabed, forming the support structure of an oil production platform.
