Pronunciation: ( jak'it),[key] —n. 1. a short coat, in any of various forms, usually opening down the front.
2. something designed to be placed around the upper part of the body for a specific purpose other than use as clothing: a life jacket. 3. a protective outer covering.
4. the skin of a potato, esp. when it has been cooked.
5. See book jacket. 6. the cover of a paperbound book, usually bearing an illustration.
7. a paper or cardboard envelope for protecting a phonograph record.
8. a metal casing, as the steel covering of a cannon, the steel cover around the core of a bullet, or the water jacket on certain types of machine guns.
9. a folded paper or open envelope containing an official document.