What does the idiom by water fountain mean?

The idiom "by the water fountain" doesn't have a commonly accepted meaning. It's likely you're thinking of a phrase that uses "water fountain" in a different context.

Here are some possibilities:

* "Meet me by the water fountain" - This is a literal instruction to meet someone at a specific location.

* "Gossip by the water cooler" - This idiom refers to casual conversation and rumors that spread in an office environment, typically around the water cooler.

* "Water fountain of youth" - This refers to a mythical source of eternal youth.

If you can provide more context about where you heard the phrase, I can help you understand its meaning more accurately.