Question

What’s the definition of windmill?

Answer 1

A windmill is a mill that converts the energy of wind into rotational energy by means of vanes called sails or blades.

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Answer 2

1) A building with sails or vanes that turn in the wind and generate power to grind grain into flour. (noun)

2) (with reference to a person's arms) move or be moved around in a circle in a manner suggestive of the rotating sails or vanes of a windmill. (verb)