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