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Phrase(s): hoist with one’s own petard
Fig. to be harmed or disadvantaged by an action of one’s own which was meant to harm someone else. (From a line in Shakespeare’s Hamlet.) • She intended to murder her brother but was hoist with her own petard when she ate the poisoned food intended for him. • The vandals were hoist with their own petard when they tried to make an emergency call from the pay phone they had broken.
McGrawhill's American Idioms And Phrasal Verbs