Because a liquid can flow, this pressure isn't only downward.

Two tubes have a liquid flowing in the same direction.

However, if the lower end is pressurised, liquid can flow from low to high.

This effect can cause liquids to flow against the force of gravity.

The cool liquid then flows back into the engine, only to be heated up again.

Sometimes a gas can be added to the liquid flowing through the evaporator.

And as the thick red liquid flowed, like curdled blood, something.

The liquid of the God Himself flowed from their eyes in moments like this.

The river of hot decaffeinated liquid flowing into my cup is a welcome relief.

In the case of a vacuum outside, there is no air pressure to push against and so the liquid could just flow from its own weight.