Would you care to elaborate on what your definition would be?

Imo, "fit" does not have to equate to muscles or ripped look of bodybuilders. As long as one is not out of shape and doing/engaging in healthy exercise/lifestyle, that's good enough for me. In this specific post, the model is lean and the pic set is of her doing yoga poses. Related https://lemmynsfw.com/post/18308580