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1. A short coat usually extending to the hips.
2. An outer covering or casing, especially:
a. The skin of a potato.
b. The dust jacket of a book or phonograph record.
c. An insulation covering for a steam pipe, wire, boiler, or similar part.
d. An open envelope or folder for filing papers.
e. The outer metal shell or case of a bullet.
3. A piece of jewelry or other ornament that attaches to an earring stud.
tr.v. jack·et·ed, jack·et·ing, jack·ets
To supply or cover with a jacket.
[Middle English jaket, from Old French jaquet, diminutive of jaque, short jacket, tunic, from jacques, nickname for French peasants, from the name Jacques; see jack.]