Bach·e·lor's but·ton Bot. A plant with flowers shaped like buttons; especially, several species of Ranunculus, and the cornflower (Centaurea cyanus) and globe amaranth (Gomphrena).
  Note: ☞ Bachelor's buttons, a name given to several flowers “from their similitude to the jagged cloathe buttons, anciently worne in this kingdom,” according to Johnson's --Gerarde, p. 472 (1633); but by other writers ascribed to “a habit of country fellows to carry them in their pockets to divine their success with their sweethearts.”
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  Blue·bot·tle, blue-bottle n.
  1. Bot. an annual Eurasian plant (Centaurea cyanus) which grows in grain fields; -- called also bachelor's button. It receives its name from its blue bottle-shaped flowers.  Varieties cultivated in North America have showy heads of blue or purple or pink or white flowers
  Syn: -- cornflower, bachelor's button.
  2. Zool. A large and troublesome species of blowfly (Musca vomitoria). Its body is steel blue.
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  Blu·ets n.  Bot. A name given to several different species of plants having blue flowers, as the Houstonia cœrulea, the Centaurea cyanus or bluebottle, and the Vaccinium angustifolium.
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  Cen·tau·re·a prop. n.  Bot. A large genus of composite plants, related to the thistles and including the cornflower or bluebottle (Centaurea Cyanus) and the star thistle (Centaurea Calcitrapa).
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  Corn·flow·er n. Bot. A conspicuous wild flower (Centaurea Cyanus), growing in grainfields.
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  Centaurea cyanus
       n : an annual Eurasian plant cultivated in North America having
           showy heads of blue or purple or pink or white flowers
           [syn: cornflower, bachelor's button, bluebottle]