Source : Webster's Revised Unabridged Dictionary (1913)

Defeasance \De*fea"sance\, n. [OF. defesance, fr. defesant, F.
   d['e]faisant, p. pr. of defaire, F. d['e]faire, to undo. See
   {Defeat}.]
   1. A defeat; an overthrow. [Obs.]

            After his foes' defeasance.           --Spenser.

   2. A rendering null or void.

   3. (Law) A condition, relating to a deed, which being
      performed, the deed is defeated or rendered void; or a
      collateral deed, made at the same time with a feoffment,
      or other conveyance, containing conditions, on the
      performance of which the estate then created may be
      defeated.