Chaff is any part of a crop that people cannot eat. this may be chopped straw, grain casings, husks, scaly flower pieces, or other plant parts in the harvest that cannot be eaten. Chaff may be fed to animals, put back in the ground to be plowed, or burned.

Grain chaff must be removed to make flour. To do this, the harvested plant must be dried and then threshed. Threshing is breaking the chaff from the grain (also called the corn). This may be done by hand, by beating it, or with a machine, as it is mainly done today. Beating the chaff away from the grain can be done with a long stick, or with a flail. A flail is two sticks connected in the middle. One stick is longer than the other. The longer stick (the handstock) is held, while the smaller stick (swipple) is hit on the crop to break the chaff away from the grain.

The threshed grain is then winnowed, which means taking away the chaff from the grain. This is usually done by wind, where the wind blows the chaff away from the threshed crop, and the grain, which is heavier than the chaff, falls into a bucket. This may be automated too.

Some crops have a tighter chaff than others. Chaff should not be confused with bran, which is a different material that covers the grain directly.

Chaff may also be made from the stalk of the crop. This is called straw chaff. Straw chaff is usually bound into a sheaf, which is a bundle of straw chaff. Like hay, these sheaves may be used as animal food, put back in the ground for plowing, or burned.