Jack·et n.
 1. A short upper garment, extending downward to the hips; a short coat without skirts.
 2. An outer covering for anything, esp. a covering of some nonconducting material such as wood or felt, used to prevent radiation of heat, as from a steam boiler, cylinder, pipe, etc.
 3. Mil. In ordnance, a strengthening band surrounding and reënforcing the tube in which the charge is fired.
 4. A garment resembling a waistcoat lined with cork, to serve as a life preserver; -- called also cork jacket.
 Blue jacket. Naut. See under Blue.
 Steam jacket, a space filled with steam between an inner and an outer cylinder, or between a casing and a receptacle, as a kettle.
 To dust one's jacket, to give one a beating. [Colloq.]


 cork jacket
      n : life preserver consisting of a sleeveless jacket of buoyant
          or inflatable design [syn: life jacket, life vest]