the name of several cruciferous plants of the genus brassica (formerly sinapis), as white mustard (b. alba), black mustard (b. nigra), wild mustard or charlock (b. sinapistrum).-a powder or a paste made from the seeds of black or white mustard, used as a condiment and a rubefacient. taken internally it is stimulant and diuretic, and in large doses is emetic.