The Collaborative International Dictionary of English v.0.48:

Turmeric \Tur"mer*ic\, n. [F. terre-m['e]rite, NL. terramerita,
   turmerica; apparently meaning, excellent earth, but perhaps a
   corruption of Ar. kurkum. Cf. Curcuma.]
   1. (Bot.) An East Indian plant of the genus Curcuma, of the
      Ginger family.
      [1913 Webster]

   2. The root or rootstock of the Curcuma longa. It is
      externally grayish, but internally of a deep, lively
      yellow or saffron color, and has a slight aromatic smell,
      and a bitterish, slightly acrid taste. It is used for a
      dye, a medicine, a condiment, and a chemical test.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Curcuma \Cur"cu*ma\ (k?r"k?-m?), n. [Cf. F., It., & Sp. curcuma;
   all fr. Ar. kurkum. Cf. Turmeric.] (Bot.)
   A genus of plants of the order Scitamine[ae], including the
   turmeric plant (Curcuma longa).
   [1913 Webster]

   Curcuma paper. (Chem.) See Turmeric paper, under
      Turmeric.
      [1913 Webster]

WordNet (r) 3.0 (2006):

Curcuma longa
    n 1: widely cultivated tropical plant of India having yellow
         flowers and a large aromatic deep yellow rhizome; source of
         a condiment and a yellow dye [syn: turmeric, Curcuma
         longa, Curcuma domestica]