Sinapine \Sin"a*pine\, n. [L. sinapi, sinapis, mustard, Gr. ???: cf. F. sinapine.] (Chem.) An alkaloid occuring in the seeds of mustard. It is extracted, in combination with sulphocyanic acid, as a white crystalline substance, having a hot, bitter taste. When sinapine is isolated it is unstable and undergoes decomposition. [1913 Webster]