Source : Webster's Revised Unabridged Dictionary (1913)

Discoid \Dis"coid\, a. [Gr. ? quoit-shaped, ? a round plate,
   quoit + ? form, shape: cf. F. disco["i]de. See {Disk}.]
   Having the form of a disk, as those univalve shells which
   have the whorls in one plane, so as to form a disk, as the
   pearly nautilus.

   {Discoid flower} (Bot.), a compound flower, consisting of
      tubular florets only, as a tansy, lacking the rays which
      are seen in the daisy and sunflower.