A Thousand Clowns (1965)

Albert: I was not aware that Nicholas was an O.W. child.
Murray: O.W.?
Albert: Out of wedlock.
Murray: For a moment there, I thought you meant prisoner of war. I think it's that natural warmth of yours, Albert, that leads me to misunderstand.

Trivia: Martin Balsam won the Academy Award for Best Supporting Actor for his role as Arnold Burns, even though he only has 10 minutes of screen time.