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

The Collaborative International Dictionary of English v.0.48:

Mexican \Mex"i*can\, prop. a.
   Of or pertaining to Mexico or its people. -- n. A native or
   inhabitant of Mexico.
   [1913 Webster]

   Mexican poppy prop. n. (Bot.), a tropical American herb of
      the Poppy family (Argemone Mexicana) with much the look
      of a thistle, but having large yellow or white blossoms.


   Mexican tea prop. n. (Bot.), an aromatic kind of pigweed
      from tropical America (Chenopodium ambrosioides).
      [1913 Webster]

WordNet (r) 3.0 (2006):

Argemone mexicana
    n 1: annual herb with prickly stems and large yellow flowers;
         southern United States to West Indies and Mexico [syn:
         Mexican poppy, Argemone mexicana]