n. In bot., Centaurea Cyanus, a composite plant, a weed in Europe, cultivated for ornament in America. Also called bluebonnet and bluecap.n. In zoology, a dipterous insect with a blue abdomen, of the family Muscidæ and genus Musca, or Calliphora. Also popularly called beef-eater and blue flesh-fly.n. A policeman, a beadle, or other officer wearing a blue dress.n. plural The grape-hyacinth, Muscari botryoides and M. racemosum. See Muscari.