For some reason I tend to confuse ARAL with URAL, but today I got to see them both together. Maybe this will help.
"Hoist by his own petard" (blown up by his own bomb) is a phrase often used incorrectly. Mostly I hear it, "hoist on
his own petard" meaning "strung up on his own flagpole." But hoist
means blown up
means, as Bonnie says, "explosive device." The expression comes from Hamlet
. I seem to remember it refers to Rosencrantz and Guildenstern with whom Hamlet gets even for their spying. There's no charge for today's lecture.