I like a lot D&D vampires. I even bought Curse of Strahd. But something I always wandered is "What is running water?"

Rivers are running waters, since it is used as an example in others editions. But how about rain (no answers are accepted on the related question)? How about a bottle? How about peeing on a vampire? How about puddles?

Related question:

Is rain considered Running Water for a Vampire's weakness?

Can the Tidal Wave spell trigger a vampire's weakness to running water?