Source : Webster's Revised Unabridged Dictionary (1913)

Tumescence \Tu*mes"cence\, n. [L. tumescens, -entis, p.pr. of
   tumescere to swell up, v. incho. fr. tumere to swell.]
   The act of becoming tumid; the state of being swollen;
   intumescence.

Source : WordNet®

tumescence
     n : tumidity resulting from the presence of blood or other fluid
         in the tissues