[pi-tahrd] 
| 1. | an explosive device formerly used in warfare to blow in a door or gate, form a breach in a wall, etc. |
| 2. | a kind of firecracker. |
| 3. | (initial capital letter ) Also called Flying Dustbin. a British spigot mortar of World War II that fired a 40-pound (18 kg) finned bomb, designed to destroy pillboxes and other concrete obstacles. |
| 4. | hoist by or with one's own petard, hurt, ruined, or destroyed by the very device or plot one had intended for another. |
To be caught in one's own trap: “The swindler cheated himself out of most of his money, and his victims were satisfied to see him hoist by his own petard.” A “petard” was an explosive device used in medieval warfare. To be hoisted, or lifted, by a petard literally means to be blown up.
"For tis the sport to haue the enginer Hoist with his owne petar" ("Hamlet" III.iv.207).See hoist.