The Collaborative International Dictionary of English v.0.48:

Recusation \Rec`u*sa"tion\ (r?k`?*z?"sh?n), n. [L. recusatio:
   cf. F. r['e]cusation.]
   1. Refusal. [Obs.]
      [1913 Webster]

   2. (Old Law) The act of refusing a judge or challenging that
      he shall not try the cause, on account of his supposed
      partiality. --Blackstone.
      [1913 Webster]

WordNet (r) 3.0 (2006):

recusation
    n 1: (law) the disqualification of a judge or jury by reason of
         prejudice or conflict of interest; a judge can be recused
         by objections of either party or judges can disqualify
         themselves [syn: recusation, recusal]
    2: (law) an objection grounded on the judge's relationship to
       one of the parties