The Collaborative International Dictionary of English v.0.48:

Poppy \Pop"py\, n.; pl. Poppies. [OE. popy, AS. popig, L.
   papaver.] (Bot.)
   Any plant or species of the genus Papaver, herbs with showy
   polypetalous flowers and a milky juice. From one species
   (Papaver somniferum) opium is obtained, though all the
   species contain it to some extent; also, a flower of the
   plant. See Illust. of Capsule.
   [1913 Webster]

   California poppy (Bot.), any yellow-flowered plant of the
      genus Eschscholtzia.

   Corn poppy. See under Corn.

   Horn poppy, or Horned poppy. See under Horn.

   Poppy bee (Zool.), a leaf-cutting bee (Anthocopa
      papaveris) which uses pieces cut from poppy petals for
      the lining of its cells; -- called also upholsterer bee.


   Prickly poppy (Bot.), Argemone Mexicana, a
      yellow-flowered plant of the Poppy family, but as prickly
      as a thistle.

   Poppy seed, the seed the opium poppy (Papaver
      somniferum).

   Spatling poppy (Bot.), a species of Silene (Silene
      inflata). See Catchfly.
      [1913 Webster] Poppy

WordNet (r) 3.0 (2006):

poppy seed
    n 1: small grey seed of a poppy flower; used whole or ground in
         baked items