online medical dictionary | definition of jacket

1. A short upper garment, extending downward to the hips; a short coat without skirts.

2. An outer covering for anything, especially. 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. In ordnance, a strengthening band surrounding and reenforcing 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.

See 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.

Origin: F. Jaquette, dim. Of jaque. See Jack.

(01 Mar 1998)