Source : Webster's Revised Unabridged Dictionary (1913)

Malaria \Ma*la"ri*a\, n. [It., contr. fr. malaaria bad air. See
   {Malice}, and Air.]
   1. Air infected with some noxious substance capable of
      engendering disease; esp., an unhealthy exhalation from
      certain soils, as marshy or wet lands, producing fevers;
      miasma.

   Note: The morbific agent in malaria is supposed by some to be
         a vegetable microbe or its spores, and by others to be
         a very minute animal blood parasite (an infusorian).

   2. (Med.) A morbid condition produced by exhalations from
      decaying vegetable matter in contact with moisture, giving
      rise to fever and ague and many other symptoms
      characterized by their tendency to recur at definite and
      usually uniform intervals.

Source : WordNet®

malaria
     n : an infective disease caused by sporozoan parasites that are
         transmitted through the bite of an infected Anopheles
         mosquito; marked by paroxysms of chills and fever