A winnowing machine is a device that separates grain from chaff by blowing air. It is commonly used in agriculture to remove the unwanted debris from food crops like wheat, rice, and corn. Other terms used to describe this machine include threshing machine, grain separator, and grain cleaner. Threshing machine is used more often for equipment that blends threshing and winnowing processes. Grain separator is a more generic term and is used to describe any machine that separates grains. Grain cleaner is often used to refer to equipment that cleans or polishes grains without separating them from their chaff or husk.