It always amazes me that FITNESS is a multi-billion dollar industry... Yet a solid, concise and universal definition of fitness is hard to nail down.
Just ask someone participating in a physical fitness program, or even someone in the fitness industry for that matter, to give you a clear definition of fitness.
You will most likely be met with the "deer caught in the headlights" stare accompanied by nonsensical stammering.
If you do get an answer, it will most likely be slanted toward the specific abilities of the person asked.
For example...