Definition of "Jacket" :

noun: (dentistry) dental appliance consisting of an artificial crown for a broken or decayed tooth

noun: a short coat

noun: an outer wrapping or casing

"Phonograph records were sold in cardboard jackets."

noun: the tough metal shell casing for certain kinds of ammunition

noun: the outer skin of a potato

verb: put a jacket on

"The men were jacketed."

verb: provide with a thermally non-conducting cover

"The tubing needs to be jacketed."