Source : Webster's Revised Unabridged Dictionary (1913)

Bachelor's button \Bach"e*lor's but"ton\, (Bot.)
   A plant with flowers shaped like buttons; especially, several
   species of {Ranunculus}, and the cornflower ({Centaures
   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.'' --Dr. Prior.

Source : WordNet®

bachelor's button
     n 1: an annual Eurasian plant cultivated in North America having
          showy heads of blue or purple or pink or white flowers
          [syn: {cornflower}, {bluebottle}, {Centaurea cyanus}]
     2: tropical American herb having rose to red or purple flowers
        that can be dried without losing color [syn: {globe
        amaranth}, {Gomphrena globosa}]