The Collaborative International Dictionary of English v.0.48:

Dropsy \Drop"sy\, n.; pl. Dropsies. [OE. dropsie, dropesie,
   OF. idropisie, F. hydropisie, L. hydropisis, fr. Gr. ?
   dropsy, fr. ? water. See Water, and cf. Hydropsy.] (Med.)
   An unnatural collection of serous fluid in any serous cavity
   of the body, or in the subcutaneous cellular tissue.
   --Dunglison.
   [1913 Webster]

WordNet (r) 3.0 (2006):

dropsy
    n 1: swelling from excessive accumulation of watery fluid in
         cells, tissues, or serous cavities [syn: edema, oedema,
         hydrops, dropsy]