Shell (?), n. 1. Something similar in form or action to an ordnance shell; specif.: (a) (Fireworks) A case or cartridge containing a charge of explosive material, which bursts after having been thrown high into the air. It is often elevated through the agency of a larger firework in which it is contained. (b) (Oil Wells) A torpedo.
2. A concave rough cast-iron tool in which a convex lens is ground to shape.
3. A gouge bit or shell bit.