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

Bouvier's Law Dictionary, Revised 6th Ed (1856):

RECUSATION, civ. law. A plea or exception by which the defendant requires
that the judge having jurisdiction of the cause, should abstain from
deciding upon the ground of interest, or for a legal objection to his
prejudice.
     2. A recusation is not a plea to the jurisdiction of the court, but
simply to the person of the judge. It may, however, extend to all the
judges, as when the party has a suit against the whole court. Poth. Proced.
Civ. 1ere part., ch. 2, s. 5. It is a personal challenge of the judge for
cause.
     3. It is a maxim of every good system of law, that a man shall not be
judge in his own cause. 2 L. R. 390; 6 L. R. 134 Ayl. Parerg. 451; Dict. de
Jur. h.t.; Merl. Repert. h.t.; vide Jacob's Intr. to the Com. Civ. and Can.
L. 11; 8 Co. 118 Dyer, 65. Dall. Diet. h.t.
     4. By recusation is also understood the challenge of jurors. Code of
Practice of Louis. art. 499, 500. Recusation is also an act, of what nature
soever it may be, by which a strange heir, by deeds or words, declares he
will not be heir. Dig. 29, 2, 95. See, generally, 1 Hopk. Ch. R. 1; 5 Mart.
Lo. R. 292; and Challenge.