The Collaborative International Dictionary of English v.0.48:

Filaria \Fi*la"ri*a\, n.; pl. filariae. [NL., fr. L. filum a
   thread.] (Zool.)
   a small, slender nematode worm of the family Onchocercidae
   (Filariidae) of many species, parasitic when adult in
   various animals, including man. They may live within the
   blood, or in other bodily fluids, or within tissues or
   cavities of the body. Infection with such organisms may be
   transmitted by blood-sucking arthropods.
   [1913 Webster +PJC]

The Collaborative International Dictionary of English v.0.48:

Filaria \Fi*la"ri*a\, n. [NL., fr. L. filum a thread.] (Zool.)
   a former genus comprised of certain nematodes, now classed as
   belonging to several genera within the family
   Onchocercidae. See Onchocerca and Guinea worm.
   [1913 Webster +PJC]

WordNet (r) 3.0 (2006):

filaria
    n 1: European weed naturalized in southwestern United States and
         Mexico having reddish decumbent stems with small fernlike
         leaves and small deep reddish-lavender flowers followed by
         slender fruits that stick straight up; often grown for
         forage [syn: redstem storksbill, alfilaria,
         alfileria, filaree, filaria, clocks, pin grass,
         pin clover, Erodium cicutarium]
    2: slender threadlike roundworms living in the blood and tissues
       of vertebrates; transmitted as larvae by biting insects