noun a plant of the genus Brassica, with yellow flowers, and linear seed pods. a powder or paste made from seeds of the mustard plant, and used as a condiment or a spice. a dark yellow colour, the colour of mustard. adjective of a dark yellow colour. Related words mustard gas See also Appendix:Colours Translation Breton: sezv collective noun sezvenn singular f (1), sezv m (2) German: Senf m Polish: musztarda f (3) Romanian: muştar n