intransitive verb
Definition: To have an unexpected or undesirable outcome, often as a result of one's actions or plans.
Example: His plan to impress her backfired when he accidentally spilled coffee on her.
noun
Definition: A situation where a plan or action has the opposite effect of what was intended, often causing problems or failures.
Example: The new policy was meant to improve productivity, but it ended up being a backfire that confused the employees.