Sin"a*pism (?), n. [L. sinapismus, Gr. &?;&?;&?;&?;, the use of a mustard blister, fr. &?;&?;&?; to apply a mustard blister, fr. &?;&?;&?;&?; mustard.] (Med.) A plaster or poultice composed principally of powdered mustard seed, or containing the volatile oil of mustard seed. It is a powerful irritant.

Sin"a*pism (?), n. [L. sinapismus, Gr. &?;&?;&?;&?;, the use of a mustard blister, fr. &?;&?;&?; to apply a mustard blister, fr. &?;&?;&?;&?; mustard.] (Med.) A plaster or poultice composed principally of powdered mustard seed, or containing the volatile oil of mustard seed. It is a powerful irritant.