If I pressed for the definition of "progression" in games, what would you give?
Amanda Cesario talked about the lack of shared economy language (deconstructions are verbose! lots of "have you played?") on a prior Game Economist Cast, and its progression feels like something that should have a more obvious definition.
Deductively, the most useful definition is "the unfolding of a game's systems design." It captures a wide range of experiences and centers the system's design as the key progression element. It also does not presuppose progression as any form of "linear" movement of elements.