That's when you feel like you continue to exhale, although there's no more air coming.
For example: If you want to hold your breath, this is easy after a deep inhalation, but very difficult after exhaling. But if you keep the feeling of exhaling, i.e. pretend to continue to exhale, it gets easier.
You can do the same with inhaling: First you inhale air, and then when you can't get more air in, you continue with the feeling of inhaling.
That exhaling or inhaling without air is quite close to a pure flow of ki.
From my understanding of it...
I appreciate the example. Your website offers much in the way of practical example and exercises as well.