The Collaborative International Dictionary of English v.0.48:

Hydrocele \Hy`dro*cele\, n. [L., fr. Gr. ?; "y`dwr water + ?
   tumor.] (Med.)
   A collection of serous fluid in the areolar texture of the
   scrotum or in the coverings, especially in the serous sac,
   investing the testicle or the spermatic cord; dropsy of the
   testicle.
   [1913 Webster]

WordNet (r) 3.0 (2006):

hydrocele
    n 1: disorder in which serous fluid accumulates in a body sac
         (especially in the scrotum)