when pigs fly
- 1Used to say that some hoped-for or promised event will never actually happen.
Like promising to do something on the day the sun rises in the west: a day that never comes.
My brother says he'll pay me back when pigs fly.
The boss will hand out raises when pigs fly, the workers grumbled.
Similarnever
Note
An impossibility used as a date: pigs have no wings, so anything scheduled for the day they fly is scheduled for never. The phrase usually closes a sentence that repeats someone's promise or hope and turns it sarcastic. It can also stand alone as a dry reply to a claim. Its force is dismissive rather than merely negative, so it suits banter and complaint more than a neutral refusal.
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Origin
The phrase plays on the fact that pigs do not have wings and cannot fly, so something said to happen 'when pigs fly' will never happen.