Windmills

Dictionary definitions give the term broader scope. My Random House Dictionary from 1980 says, "A machine driven by the wind blowing against a wheel of blades attached to a shaft, used chiefly for pumping water."

An online dictionary says:

a : a mill or machine operated by the wind usually acting on oblique vanes or sails that radiate from a horizontal shaft; especially : a wind-driven water pump or electric generator
b : the wind-driven wheel of a windmill
http://www.merriam-webster.com/dictionary/windmill

Of course, voters are free to rate images based on their own interpretation of the challenge's title, description, and rules, and some may give a bonus to images depicting a machine designed to crush grain.