Source : Webster's Revised Unabridged Dictionary (1913)

Jacket \Jack"et\, n. [F. jaquette, dim. of jaque. See 3d {Jack},
   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
      re["e]nforcing 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.]

Source : WordNet®

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