[for the weather] to spoil something by raining. Oh, the weather looks awful. I hope it doesn't rain the picnic out.It's starting to sprinkle now. Do you think it will rain out the ball game?
Force the cancellation or postponement of some event owing to bad weather. For example, Our picnic was rained out, but we hope to have it next week. [1920s]
To force the cancellation or postponement of some event because of rain. Used chiefly in the passive: If the parade is rained out, it will be held the following week.