Sentence:  Turbines have been around for a long time—windmills and water wheels are early examples. The name comes from the Latin "turbo", meaning "vortex", and thus the <WSD>defining</WSD> property of a turbine is that a fluid or gas turns the blades of a rotor, which is attached to a shaft that can perform useful work. 
Meaning of the word marked with <WSD> tags:  To determine with precision; to mark out with distinctness; to ascertain or exhibit clearly.