be hoist by (one's) own petard(redirected from be hoist by their own petard)
be 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.