Source : Webster's Revised Unabridged Dictionary (1913)

Expert \Ex*pert"\, a. [F. expert, L. expertus, p. p. of experiri
   to try. See {Experience}.]
   Taught by use, practice, or experience, experienced; having
   facility of operation or performance from practice; knowing
   and ready from much practice; clever; skillful; as, an expert
   surgeon; expert in chess or archery.

         A valiant and most expert gentleman.     --Shak.

         What practice, howsoe'er expert In fitting aptest words
         to things . . . Hath power to give thee as thou wert?
                                                  --Tennison.

   Syn: Adroit; dexterous; clever; ready; prompt.

Expert \Ex"pert\, n.
   1. An expert or experienced person; one instructed by
      experience; one who has skill, experience, or extensive
      knowledge in his calling or in any special branch of
      learning.

   2. (Law)
      (a) A specialist in a particular profession or department
          of science requiring for its mastery peculiar culture
          and erudition.

   Note: Such specialists may be witnesses in matters as to
         which ordinary observers could not without such aid
         form just conclusions, and are liable for negligence in
         case they injure another from want of proper
         qualifications or proper care in the exercise of their
         specialty.
      (b) A sworn appraiser.

Expert \Ex*pert"\, v. t.
   To experience. [Obs.]

         Die would we daily, once it to expert.   --Spencer.

Source : WordNet®

expert
     adj : having or showing knowledge and skill and aptitude; "adept
           in handicrafts"; "an adept juggler"; "an expert job";
           "a good mechanic"; "a practiced marksman"; "a
           proficient engineer"; "a lesser-known but no less
           skillful composer"; "the effect was achieved by
           skillful retouching" [syn: {adept}, {good}, {practiced},
            {proficient}, {skillful}, {skilful}]

expert
     n : a person with special knowledge or ability who performs
         skillfully