The Collaborative International Dictionary of English v.0.48:

Clairvoyant \Clair*voy"ant\, a. [F., fr. clair clear + voyant,
   p. pr. of voir to see. See Clear, and Vision.]
   Pertaining to clairvoyance; discerning objects while in a
   mesmeric state which are not present to the senses.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Clairvoyant \Clair*voy"ant\ n.
   One who is able, when in a mesmeric state, to discern objects
   not present to the senses.
   [1913 Webster] Clake

WordNet (r) 3.0 (2006):

clairvoyant
    adj 1: perceiving things beyond the natural range of the senses
    2: foreseeing the future [syn: clairvoyant, precognitive,
       second-sighted]
    n 1: someone who has the power of clairvoyance

The Devil's Dictionary (1881-1906):

CLAIRVOYANT, n.  A person, commonly a woman, who has the power of
seeing that which is invisible to her patron, namely, that he is a
blockhead.