The answer that one gives when asked a question that one either does not know or simply does not want to give an answer to. This response hails from the 'Churchill' car insurance advert in which their mascot dog (Named Churchill) is being asked questions. He gives the answer "CRANKSHAFT" before the lady asking the question has finished speaking.
A: "Do any of you know where my keys are?"
A: "What should I do in the event of a fire?"