Source : Webster's Revised Unabridged Dictionary (1913)

Tumefaction \Tu`me*fac"tion\, n. [Cf. F. tum['e]faction.]
   The act or process of tumefying, swelling, or rising into a
   tumor; a swelling. --Arbuthnot.

Source : WordNet®

tumefaction
     n : the process of tumefying; the organic process whereby tissue
         becomes swollen by the accumulation of fluid within it