(1) Displaying great versatility or variety. (2) Able to take on many different forms or natures.
Example:
He was attempting to become the protean athlete with contracts to play professional baseball, football, and basketball.
Proteus was the figure in the Odyssey who revealed to Menelaus how to get home to Sparta with the notorious Helen of Troy. Before he would give up the information, though, Menelaus had to capture him -- no mean feat, since he had the ability to change into any natural shape he chose. The word protean came to describe this ability to change into many different shapes or to play many different roles in quick succession.