roughage

Meanings

1. Originally (archaic), garbage, rubbish, or waste; later (agriculture) the portions of a crop which are discarded, such as husks, stalks, etc.; also, agricultural waste such as weeds.
2. Coarse or rough plant material such as hay and silage used as animal fodder.
3. Substances, generally of plant origin, consisting mostly of complex carbohydrates which are undigested when eaten by humans, and which therefore help the passage of food and waste through the alimentary tract; dietary fibre.

Etymology

From rough (“not smooth; crude, unrefined”) + -age (suffix forming nouns with the sense of appurtenance or collection).