American Heritage Dictionary
(3)
Century Dictionary
(2)
GNU Webster's 1913
(1)
WordNet
(4)
Elsewhere on the web
It's a kind of fitness, and it comes only with practice.— WordPress.com News
I feel like, you know, that my fitness is at my best right now.— IBN Top Headlines
He also has put a lot of work into his fitness, which is clearly paying dividends.— Forty Deuce
Male mate-fitness, therefore, involves proofs of fidelity - the reason women are fixated on being loved - and proofs of strength - the reason they select for status.— 1. MajorityRights.com (main blog)

Century Dictionary (1)
Bubble size: how much this word was used in a year
Bubble height: used more or less than expected, vs. all uses evenly distributed
You can expect to see this word a few times a week.