When pigs fly" is an adynaton, a way of saying that something will never happen. The phrase is often used for humorous effect, to scoff at over-ambition. There are numerous variations on the theme; when an individual with a reputation for failure finally succeeds, onlookers may sarcastically claim to see a flying pig. ("Hey look! A flying pig!")  Other variations on the phrase include "And pigs will fly," this one in retort to an outlandish statement.
An example occurs in the film The Eagle Has Landed: an Irish secret agent working for the Nazis replies to a German general speaking of Germany's shortly winning World War II, "Pigs may fly, general, but I doubt it!" Later, when the Irishman sees German soldiers parachuting before an attack, he says to himself, "Mother of God! Flying pigs!"
btw thanks wikipedia
You are not logged in. If you sign up for an account,
you can gain additional voting power over time, allowing your vote to have an even
greater impact on submission scores!