He is a sexist 'pig'. = He is a 'male chauvinist pig'. [=he is a man who thinks women are not equal to men]
The train station will be renovated 'when pigs fly'. [=it will never be renovated]
“This time I think he'll ask me to marry him!” “Yeah, and 'pigs might fly'.”
(..) -You don't know how to be a husband! -Sit down before I-- Do we ever go anywhere without having thugs... hanging around aII the time? I have Nick ''The Pig'' as a friend. What kind of Iife is that? Can't you see... what we're becoming, Tony? We're Iosers. -Go home. You're stoned. (..)1983 Scarface
(..) Look. He's a reaI ! You know what a is? No, Frank, you teII me. What is a ? It's the Yiddish word for ''pig.'' A guy who wants more than he needs. He don't fIy straight no more. So, it comes down to one thing, Tony boy, and you never forget it. Lesson Number : (..)1983 Scarface