pl. [ from the pigment phycocyanin. ] any of a group of photosynthetic autotrophic prokaryotic microorganisms possessing characteristics of both bacteria and plants. When classed as bacteria, they are assigned to the Cyanobacteria; when classed as plants, they are assigned to the Cyanophyta. They were earlier named blue-green algae, a term less used now in technical discussions. Since the chlorophyll within the cyanobacteria is diffused throughout the cell, rather than being contained in chloroplasts, they are no longer thought of as true plants. [ PJC ]

n. [ Gr. ky`anos a dark blue substance + -gen: cf. F. cyanogène. So called because it produced blue dyes. ] (Chem.) A colorless, inflammable, poisonous gas, C2N2, with a peach-blossom odor, so called from its tendency to form blue compounds; obtained by heating ammonium oxalate, mercuric cyanide, etc. It is obtained in combination, forming an alkaline cyanide when nitrogen or a nitrogenous compound is strongly ignited with carbon and soda or potash. It conducts itself like a member of the halogen group of elements, and shows a tendency to form complex compounds. The name is also applied to the univalent radical, CN (the half molecule of cyanogen proper), which was one of the first compound radicals recognized. [ 1913 Webster ]

☞ Cyanogen is found in the commercial substances, potassium cyanide, or prussiate of potash, yellow prussiate of potash, Prussian blue, Turnbull's blue, prussic acid, etc. [ 1913 Webster ]

n. [ Gr. ky`anos a dark blue substance + -meter: cf. F. cyanomètre. ] An instrument for measuring degress of blueness. [ 1913 Webster ]

n. [ Gr. ky`anos a dark blue substance + pa`qos affection. ] (Med.) A disease in which the body is colored blue in its surface, arising usually from a malformation of the heart, which causes an imperfect arterialization of the blood; blue jaundice. [ 1913 Webster ]

n. [ Gr. ky`anos a dark blue substance + fy`llon leaf. ] (Bot.) A blue coloring matter supposed by some to be one of the component parts of chlorophyll. [ 1913 Webster ]

a. [ See Cyanic. ] Rendered blue, as the surface of the body, from cyanosis or deficient aëration of the blood. [ 1913 Webster ]

‖n. [ NL. See Cyanic. ] (Med.) A condition in which, from insufficient aëration of the blood, the surface of the body becomes blue. See Cyanopathy. [ 1913 Webster ]

n. [ See Cyanic. ] (Min.) Native sulphate of copper. Cf. Blue vitriol, under Blue. [ 1913 Webster ]

a. (Med.) Relating to cyanosis; affected with cyanosis; as, a cyanotic patient; having the hue caused by cyanosis; as, a cyanotic skin. [ 1913 Webster ]

n. [ Cyanide + -type. ] A photographic picture obtained by the use of a cyanide. [ 1913 Webster ]