A term coined by Kenneth Folk in his excellent short book Contemplative Fitness, which is freely available online and only a couple of hours' read.

Relevant excerpts on this definition:

Just as we can speak of physical fitness and mental fitness, we can identify a branch of human development that we might call contemplative fitness. Contemplative fitness has to do with the kind of growth that comes from meditation and related contemplative practices.

Its ultimate manifestation is a kind of persistent well-being that is independent of external circumstances. At its essence, contemplative fitness is the art of being OK.