The Collaborative International Dictionary of English v.0.48:

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; -- applied especially to the state of swelling
   of the vascular tissue in the male and female sex organs when
   they have been stimulated to readiness for sexual
   intercourse.
   [Webster 1913 Suppl. +PJC]

WordNet (r) 3.0 (2006):

tumescence
    n 1: tumidity resulting from the presence of blood or other
         fluid in the tissues

Moby Thesaurus II by Grady Ward, 1.0:

101 Moby Thesaurus words for "tumescence":
   access, accession, accretion, accrual, accruement, accumulation,
   addition, advance, aggrandizement, amplification, appreciation,
   ascent, augmentation, ballooning, bloat, bloatedness, bloating,
   blowing up, boil, boom, boost, broadening, buildup, bump, bunion,
   carbuncle, corn, crescendo, cyst, development, diastole,
   dilatation, dilation, distension, dropsy, edema, elevation,
   enlargement, expansion, extension, flatulence, flatulency, flatus,
   flood, furuncle, gain, gassiness, greatening, growth, gush, hike,
   increase, increment, inflation, intumescence, jump, leap, lump,
   meteorism, mounting, multiplication, pimple, pock, productiveness,
   proliferation, puff, puffiness, puffing, pustule, raise, rise,
   rising, sebaceous cyst, snowballing, spread, stretching, surge,
   swell, swellage, swelling, swollenness, tumefaction, tumidity,
   tumidness, tumor, turgescence, turgescency, turgidity, turgidness,
   tympanism, tympany, up, upping, upsurge, upswing, uptrend, upturn,
   waxing, wen, widening, windiness