The Collaborative International Dictionary of English v.0.48:

Expert \Ex*pert"\ ([e^]ks*p[~e]rt"), 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.
   [1913 Webster]

         A valiant and most expert gentleman.     --Shak.
   [1913 Webster]

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

   Syn: Adroit; dexterous; clever; ready; prompt.
        [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

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.
      [1913 Webster]

   2. (Law)
      (a) A specialist in a particular profession or department
          of science requiring for its mastery peculiar culture
          and erudition.
          [1913 Webster]

   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.
          [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Expert \Ex*pert"\, v. t.
   To experience. [Obs.]
   [1913 Webster]

         Die would we daily, once it to expert.   --Spencer.
   [1913 Webster]

WordNet (r) 3.0 (2006):

expert
    adj 1: 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, expert, good, practiced,
           proficient, skillful, skilful]
    2: of or relating to or requiring special knowledge to be
       understood; "technical terminology"; "a technical report";
       "technical language" [syn: technical, expert]
    n 1: a person with special knowledge or ability who performs
         skillfully

Moby Thesaurus II by Grady Ward, 1.0:

202 Moby Thesaurus words for "expert":
   Admirable Crichton, Daedalian, Dutch uncle, Polonius, accomplished,
   ace, acquainted with, adept, adept in, admonisher, adroit, adviser,
   aficionado, amateur, apt, arbiter, arbiter elegantiarum,
   arbiter of taste, archetypical, artisan, artist, artiste, artistic,
   at home in, at home with, attache, au fait, authoritative,
   authority, backseat driver, bon vivant, bravura, brilliant, buff,
   buttinsky, championship, classic, clean, clever, cognoscente,
   collector, confidant, confined, connaisseur, connoisseur,
   consultant, consummate, conversant with, coordinated, cordon bleu,
   counsel, counselor, crack, crack shot, crackerjack, craftsman,
   critic, cunning, cute, dab, dabster, daedal, darb, dead shot, deft,
   developed, dexterous, dextrous, dilettante, diplomat, diplomatic,
   diplomatist, doyen, elder statesman, epicure, epicurean, excellent,
   exemplary, experienced, experienced hand, experimental scientist,
   expert at, expert consultant, familiar with, fan, fancy, feature,
   featured, finished, first-rate, freak, fully developed, good,
   good at, good judge, goodish, gourmand, gourmet, graceful,
   graduate, guide, handy, handy at, handy man, informed in,
   ingenious, instructor, intellectual, intimate with, journeyman,
   judge, kibitzer, knowledgeable, learned, limited, magisterial,
   man of science, marksman, master, master of, masterful, masterly,
   mature, matured, maven, meddler, mentor, model, monitor, neat,
   nestor, no mean, no slouch, nut, orienter, past master, perfected,
   polished, politic, politician, practical scientist, preceptist,
   pro, professional, professor, proficient, proficient in, pundit,
   qualified, quick, quintessential, quite some, ready, refined,
   refined palate, resourceful, restricted, ripe, ripened, savant,
   scholar, schooled, scientist, shark, sharp, skilled, skilled in,
   skillful, slick, some, specialist, specialistic, specialized,
   statesman, statesmanlike, strong in, stylish, superb, superior,
   swell, tactful, teacher, technical, technical adviser,
   technical expert, technician, technologist, the compleat,
   the complete, top-notch, trained, up on, versed in, virtuoso,
   well up on, well-done, well-read in, well-versed, whiz, wizard,
   wonderful, workmanlike