"What is running water?" in respect to D&D vampires?

Rivers are considered to be running water, as they are 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?