Source : Webster's Revised Unabridged Dictionary (1913)

Professional \Pro*fes"sion*al\, a.
   1. Of or pertaining to a profession, or calling; conforming
      to the rules or standards of a profession; following a
      profession; as, professional knowledge; professional
      conduct. ``Pride, not personal, but professional.''
      --Macaulay. ``A professional sneerer.'' --De Quincey.

   2. Engaged in by professionals; as, a professional race; --
      opposed to {amateur}.

Professional \Pro*fes"sion*al\, n.
   A person who prosecutes anything professionally, or for a
   livelihood, and not in the character of an amateur; a
   professional worker.

Source : WordNet®

professional
     adj 1: engaged in a profession or engaging in as a profession or
            means of livelihood; "the professional man or woman
            possesses distinctive qualifications"; "began her
            professional career after the Olympics"; "professional
            theater"; "professional football"; "a professional
            cook"; "professional actors and athletes" [ant: {nonprofessional}]
     2: of or relating to or suitable as a profession; "professional
        organizations"; "a professional field such as law"
     3: characteristic of or befitting a profession or one engaged
        in a profession; "professional conduct"; "professional
        ethics"; "a thoroughly professional performance" [ant: {unprofessional}]
     4: of or relating to a profession; "we need professional
        advice"; "professional training"; "professional equipment
        for his new office"
     5: engaged in by members of a profession; "professional
        occupations include medicine and the law and teaching"

professional
     n 1: a person engaged in one of the learned professions [syn: {professional
          person}]
     2: an athlete who plays for pay [syn: {pro}] [ant: {amateur}]
     3: an authority qualified to teach apprentices [syn: {master}]