I thought it could be helpful to talk about flow in the context of mtb. Flow is kinda self-explanatory as a general concept, but can have the specific meaning of being able to ride a line with minimal or no pedalling. So a rhythm line can flow, for instance. Likewise, there's a xc trail near me with lots of g-outs that, while you have to pedal aggressively on some sections, is close to a single-speed trail, has nice flow, and has sections that really reward riding aggressively with non-pedalling inputs -- the better you do this, the more those specific lines flow.
Flow, like pumping, is also consciousness, a different way of looking at trails. Rocks can either be scary things you ride around, or things you look to pump and that add to flow.