The Collaborative International Dictionary of English v.0.48:

Megalocyte \Meg"a*lo*cyte\, n. [Megalo- + Gr. ? a hollow
   vessel.] (Physiol.)
   A large, flattened red blood cell corpuscle having no
   nucleus, twice the diameter of the ordinary red corpuscle,
   found in considerable numbers in the blood in profound
   anaemia.
   [1913 Webster]

WordNet (r) 3.0 (2006):

megalocyte
    n 1: abnormally large red blood cell (associated with pernicious
         anemia) [syn: megalocyte, macrocyte]