hoist by your own petard

hoist by (one's) own petard

To be injured, ruined, or defeated by one's own action, device, or plot that was intended to harm another; to have fallen victim to one's own trap or schemes. (Note: "hoist" in this instance is the simple past-tense of the archaic form of the verb, "hoise.") I tried to get my boss fired by planting drugs on him, but I was hoist by my own petard when the police caught me with them beforehand.
See also: hoist, own, petard

hoist by your own petard

or

hoist with your own petard

FORMAL
If someone is hoist by their own petard or is hoist with their own petard, something they do to get an advantage or to harm someone else results in harm to themselves. You should stop spreading stories about your opponents or, sooner or later, you will be hoist with your own petard. Note: `Petards' were metal balls filled with gunpowder which were used to blow up walls or gates. The gunpowder was lit by a slow-burning fuse, but there was always a danger that the device would explode too soon and `hoist' the person lighting it, that is, blow them up in the air.
See also: hoist, own, petard

hoist by your own petard

Hurt by your own misdeed. A petard was a medieval bomb made of a container of gunpowder with a fuse, and to blow open gates during sieges against towns and fortresses. Unreliable, petards often exploded prematurely and sent the person who lit the fuse aloft (the “hoist” image) in one or more pieces. The phrase, which is often misquoted as “hoist on one's own petard,” comes from Hamlet: For 'tis the sport to have the engineer Hoist with his own petard; and ‘t shall go hard But I will delve one yard below their mines And blow them at the moon . . .
See also: hoist, own, petard