The Collaborative International Dictionary of English v.0.48:

Jacket \Jack"et\, n. [F. jaquette, dim. of jaque. See 3d Jack,
   n.]
   [1913 Webster]
   1. A short upper garment, extending downward to the hips; a
      short coat without skirts.
      [1913 Webster]

   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.
      [1913 Webster]

   3. (Mil.) In ordnance, a strengthening band surrounding and
      re["e]nforcing the tube in which the charge is fired.
      [1913 Webster]

   4. A garment resembling a waistcoat lined with cork, to serve
      as a life preserver; -- called also cork jacket.
      [1913 Webster]

   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.]
      [1913 Webster]

WordNet (r) 3.0 (2006):

cork jacket
    n 1: life preserver consisting of a sleeveless jacket of buoyant
         or inflatable design [syn: life jacket, life vest,
         cork jacket]