Whenever I hear the phrase...

"they were out playing ball"

...I would automatically assume baseball, but I just wondered if that was common, or perhaps regional, or based on some other factor.

How about other people? Is it just baseball to you? Is it some other specific sport like basketball or futbol? Or do you not understand it to refer to any specific sport, and would then ask the speaker, "what were they playing?" ?

Well, when my fiancee says he's going to go "play some ball" he means basketball.



Of course we live in the basketball capitol of the World-INDIANA!

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Those who can make you believe absurdities can make you commit atrocities.
~Voltaire

Associatively, that conjurs up in my head: baseball, basketball, and soccer.

Also institutional corruption ([corruptor to potential corruptee]: "if you don't want to play ball, we'll find someone who does.").

So, I voted Does not imply a specific sport.

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The pedigree of honey
Does not concern the bee;
A clover, any time, to him
Is aristocracy. ~Emily Dickinson

Would you not assume that such a statement would be used mostly (not entirely) among people familiar with one another and they would know?

I have heard football, baseball and basketball referred to as "playing ball."

At the same time, at least in my day, it was football and shooting or playing hoops and baseball was most commonly the only sport referred to as "ball."

What does the umpire state at the start of the game and every inning?

"Play ball" is the offical signal to begin playing the game.

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“The only thing necessary for the triumph of evil is for good men to do nothing” - Edmund Burke

Pocket pool.