Petard,

Petard, an instrument for blowing open the gates of a fortress, demolishing palisades, &c., consisting of a half-cone of thick iron filled with powder and ball; this was firmly fastened to a plank, and the latter was provided with hooks to allow of its being attached securely to a gate, &c. The petard, which was lighted by a slow-match, was superseded by the use of powder-bags. Large petards contained as much as 13 lb. of powder. See BOMB, and SHELL.