mustard oil

noun

1

: a colorless to pale yellow pungent irritating essential oil that is obtained by distillation from the seeds usually of black mustard after expression of the fatty oil and maceration with water, that consists largely of allyl isothiocyanate, and that is used especially in liniments and medicinal plasters compare sinigrin

2

a

: allyl isothiocyanate

b

: an isothiocyanate ester