Suitable, proper.
Example: "You have nothing to say about it. i'll do exactly as i see fit."
Adapted to a purpose or environment.
Example: "Survival of the fittest"
In good shape; physically well.
Example: "You don't have to be a good climber for kilimanjaro, but you do have to be fit."
Sexually attractive; good-looking; fanciable.
Example: "I think the girl working in the office is fit."
Prepared; ready.