not over till/until the fat lady sings

not over till/until the fat lady sings

The final outcome cannot be assumed or determined until a given situation, event, etc., is completely finished. The phrase refers to the stereotypically stout female sopranos of the opera, particularly the Valkyrie Brünnehilde, whose aria concludes Richard Wagner's opera cycle Der Ring des Nibelungen. It is often used in reference to organized competitions, such as sporting events, political elections, etc. A: "We're down by six points with only two minutes remaining. There's no way we can win now!" B: "Hey, it's not over till the fat lady sings!" It doesn't seem likely that the senator will be elected to another term, but it isn't over until the fat lady sings.
See also: fat, lady, not, over, sing, till, until
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.