The Collaborative International Dictionary of English v.0.48:

Voidance \Void"ance\, n.
   1. The act of voiding, emptying, ejecting, or evacuating.
      [1913 Webster]

   2. (Eccl.) A ejection from a benefice.
      [1913 Webster]

   3. The state of being void; vacancy, as of a benefice which
      is without an incumbent.
      [1913 Webster]

   4. Evasion; subterfuge. [Obs.] --Bacon.
      [1913 Webster]

WordNet (r) 3.0 (2006):

voidance
    n 1: the act of removing the contents of something [syn:
         emptying, voidance, evacuation]