petard

It was indeed a clever plan to entrap his opponent, but in the end he was hoist by his own petard.

hoist with his own petard

to be caught in one's own petard

to blow oneself up with one's own petard

to be hoist by one's own petard

It was always appealing when a character is hoist on his own petard.

Listeners, I capitulated in the two minutes we were on break and I did Google petard.

Listeners, you should write in and tell us, what is a petard?

In any case, I don't even know if I'm saying petard right.

How's that? How did I do? Do you know what a petard is?

And in the case of Icahn, this gives me an excuse to use a phrase which I've long wanted to use, which is hoisted by his own petard.

How I picture a petard is some kind of medieval weapon that's sort of like a spear or a halberd or a pike, and that somehow you're hoisted on it in some kind of jousting accident.