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."