Entry 1 sense Webster, 1913 Prussiate · Prus·si·ate · IPA 01 n. A salt of prussic acid; a cyanide. 1. A salt of prussic acid; a cyanide.(Chem.) Phrases & compounds Red prussiate of potash — See Potassium ferricyanide, under Ferricyanide. Yellow prussiate of potash — See Potassium ferrocyanide, under Ferrocyanide.