The Collaborative International Dictionary of English v.0.48:

Percipient \Per*cip"i*ent\, a. [L. percipiens, -entis, p. pr. of
   percipere. See Perceive.]
   Having the faculty of perception; perceiving; as, a
   percipient being. --Bentley. -- n. One who, or that which, is
   percipient. --Glanvill.
   [1913 Webster]

WordNet (r) 3.0 (2006):

percipient
    adj 1: characterized by ease and quickness in perceiving; "clear
           mind"; "a percipient author" [syn: clear, percipient]
    n 1: a person who becomes aware (of things or events) through
         the senses [syn: perceiver, percipient, observer,
         beholder]