- [Bot] The name of several cruciferous plants of the genus Brassicaformerly Sinapis), as white mustard Brassica alba), black mustard Brassica Nigra), wild mustard or charlock Brassica 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.
Note: ☞ There are also many herbs of the same family which are called mustard, and have more or less of the flavor of the true mustard; as, bowyer's mustard (Lepidium ruderale); hedge mustard (Sisymbrium officinale); Mithridate mustard (Thlaspi arvense); tower mustard (Arabis perfoliata); treacle mustard (Erysimum cheiranthoides).
Etymology: OF. moustarde, F. moutarde, fr. L. mustum must, -- mustard was prepared for use by being mixed with must. See Must (n.)