petarded

A portmanteauof "retarded" and "petard," it describes a plan backfiring on you in such a way that you are left looking utterly ridiculous. It combines the concept of retarded--which is to say mentally deficient--and the phrase "hoisted by your own petard," which means to have damage done to you by the means you had intended to employ to damage others. A petard is an explosive used to break down barricades in warfare, and so petarded can also mean "blown up," in some circumstances.