When pigs fly humorous spoken language informal
Pig might fly, flying pig or when pigs can fly are alternatives of When pigs fly. "Do you think we will pass the English final exam without any revision?". "Yes, and pigs might fly/ flying pig."
You said you could jump higher than a towel? Common, flying pig.
Iran said that he won a billion lottery ticket? I will believe it when pigs fly. Nobody doesn't know he is such a joker
I will vote for Donald Trump for this Presidential term of office when pigs fly.
Don't make plans that depend on something hoped before it has actually happened.
Don't make sure that the result will be good until it actually happens.
Used to implicate utter incredulity in something said or believed by someone else.
To express that you don't believe in something that someone has just said
This form of the expression was first used two hundred years ago as a sarcastic rejoinder to any overly optimistic prediction made by the gullible. It is pigs that have stood the test of time as the favoured image of an animal that is particularly unsuited to flight.
To do something in an unusual way
I guess I like to run against the grain in everything I do.