The Collaborative International Dictionary of English v.0.48:
Jacket \Jack"et\, n. [F. jaquette, dim. of jaque. See 3d Jack,
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.]