means A machine that uses sails or blades turned by the wind to power work like grinding grain, pumping water, or generating electricity.

from A plain English compound of "wind" and "mill," both old Germanic words — "mill" traces back through Old English "mylen" to Latin "molina," from "molere," to grind. The word names exactly what the thing first did: a mill driven by wind, built across medieval Europe to spare human and animal muscle from the endless turning of the grindstone.