- noun a biennial plant with hairy leaves and seeds that produce an oil which is used by the pharmaceutical industry
- A hardy biennial plant, Oenothera biennis, growing to 2 m with large yellow flowers. The seeds are the source of evening primrose oil which contains a high proportion of gamma linoleic acid, a precursor of many important body chemicals and used as a health supplement and prophylactic. The leaves and stems were once used as a popular food by North Native Americans. The root may be boiled and eaten either pickled or as a salad vegetable.