Definitions of jacket:

• noun:   a short coat
• noun:   an outer wrapping or casing

  Example: "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
• noun:   (dentistry) an artificial crown fitted over a broken or decayed tooth
• verb:   put a jacket on

  Example: "The men were jacketed"

• verb:   provide with a thermally non-conducting cover

  Example: "The tubing needs to be jacketed"