The Collaborative International Dictionary of English v.0.48:

Asafetida \As`a*fet"i*da\, Asafoetida \As`a*f[oe]t"i*da\, n.
   [Asa + L. foetidus fetid.]
   The fetid gum resin or inspissated juice of a large
   umbelliferous plant (Ferula asafoetida) of Persia and the
   East Indies. It is used in medicine as an antispasmodic.
   [Written also assafoetida.]
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Ferula \Fer"u*la\, n. [L. ferula giant fennel (its stalks were
   used in punishing schoolboys), rod, whip, fr. ferire to
   strike; akin to OHG. berjan, Icel. berja. Cf. Ferule.]
   1. A ferule. [Obs.] --Beau. & Fl.
      [1913 Webster]

   2. The imperial scepter in the Byzantine or Eastern Empire.
      [1913 Webster]

   3. [capitalized] A genus of plants of the parsley family
      Apiaceae (of the order Umbelliferae), including some
      yielding asafetida. Members include Ferula asafoetida
      (Ferula foetida), the giant fennel (Ferula communis),
      and Ferula orientalis.
      [PJC]

WordNet (r) 3.0 (2006):

asafetida
    n 1: the brownish gum resin of various plants; has strong taste
         and odor; formerly used as an antispasmodic [syn:
         asafetida, asafoetida]