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 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.