cyanide рдХреНрдпрд╛ рд╣реИрдВ? cyanide рдХреНрдпрд╛ рд╣реИрдВ? Any of various salts or esters of hydrogen cyanide containing a CN group, especially the extremely poisonous compounds potassium cyanide and sodium cyanide.To treat (a metal surface) with cyanide to produce a hard surface.To treat (an ore) with cyanide to extract gold or silver.