One of the minute papillary processes on certain vascular membranes; a villosity; as, villi cover the lining of the small intestines of many animals and serve to increase the absorbing surface.
- Biology A minute projection arising from a mucous membrane, especially:
- Biology One of the numerous vascular projections of the small intestine.
- Biology One of the fingerlike projections of the chorion that contribute to the formation of the placenta in mammals.
- Botany A fine, hairlike epidermal outgrowth.