The Collaborative International Dictionary of English v.0.48:

Feverfew \Fe"ver*few\ (f[=e]"v[~e]r*f[=u]), n. [AS. feferfuge,
   fr. L. febrifugia. See fever, Fugitive, and cf.
   Febrifuge.] (Bot.)
   A perennial plant (Pyrethrum Parthenium, or Chrysanthemum
   Parthenium) allied to camomile, having finely divided leaves
   and white blossoms; -- so named from its supposed febrifugal
   qualities.
   [1913 Webster]

WordNet (r) 3.0 (2006):

feverfew
    n 1: bushy aromatic European perennial herb having clusters of
         buttonlike white-rayed flower heads; valued traditionally
         for medicinal uses; sometimes placed in genus Chrysanthemum
         [syn: feverfew, Tanacetum parthenium, Chrysanthemum
         parthenium]