petard /pĭ-tärd′/
noun
A small bell-shaped bomb used to breach a gate or wall. A loud firecracker. A case containing powder to be exploded, esp. a conical or cylindrical case of metal filled with powder and attached to a plank, to be exploded against and break down gates, barricades, drawbridges, etc. It has been superseded. A small, hat-shaped explosive device, used to blow a hole in a door or wall. Anything potentially explosive, in a non-literal sense. An explosive device used to break down a gate or wall.
idiom
(be hoist with one's own petard) To be undone by one's own schemes.
verb
To attack or blow a hole in (something) with a petard.
The American Heritage® Dictionary of the English Language, 5th Edition
