The Collaborative International Dictionary of English v.0.48:

Extravasation \Ex*trav`a*sa"tion\, n. [Cf. F. extravasation.]
   1. The act of forcing or letting out of its proper vessels or
      ducts, as a fluid; effusion; as, an extravasation of blood
      after a rupture of the vessels.
      [1913 Webster]

   2. (Geol.) The issue of lava and other volcanic products from
      the earth.
      [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

extravasation
    n 1: an extravasated liquid (blood or lymph or urine); the
         product of extravasation
    2: (of volcanos) pouring out fumes or lava (or a deposit so
       formed) [syn: eruption, eructation, extravasation]
    3: the process of exuding or passing out of a vessel into
       surrounding tissues; said of blood or lymph or urine