Wrong Thing n.

A design, action, or decision that is clearly incorrect or inappropriate. Often capitalized; always emphasized in speech as if capitalized. The opposite of the Right Thing; more generally, anything that is not the Right Thing. In cases where `the good is the enemy of the best', the merely good -- although good -- is nevertheless the Wrong Thing. "In C, the default is for module-level declarations to be visible everywhere, rather than just within the module. This is clearly the Wrong Thing."

--The Jargon File version 4.3.1, ed. ESR, autonoded by rescdsk.