The Collaborative International Dictionary of English v.0.48:

Profession \Pro*fes"sion\, n. [F., fr. L. professio. See
   Profess, v.]
   1. The act of professing or claiming; open declaration;
      public avowal or acknowledgment; as, professions of
      friendship; a profession of faith.
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            A solemn vow, promise, and profession. --Bk. of Com.
                                                  Prayer.
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   2. That which one professed; a declaration; an avowal; a
      claim; as, his professions are insincere.
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            The Indians quickly perceive the coincidence or the
            contradiction between professions and conduct. --J.
                                                  Morse.
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   3. That of which one professed knowledge; the occupation, if
      not mechanical, agricultural, or the like, to which one
      devotes one's self; the business which one professes to
      understand, and to follow for subsistence; calling;
      vocation; employment; as, the profession of arms; the
      profession of a clergyman, lawyer, or physician; the
      profession of lecturer on chemistry.
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            Hi tried five or six professions in turn.
                                                  --Macaulay.
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   Note: The three professions, or learned professions, are,
         especially, theology, law, and medicine.
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   4. The collective body of persons engaged in a calling; as,
      the profession distrust him.
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   5. (Eccl. Law.) The act of entering, or becoming a member of,
      a religious order.
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WordNet (r) 3.0 (2006):

profession
    n 1: the body of people in a learned occupation; "the news
         spread rapidly through the medical profession"; "they
         formed a community of scientists"
    2: an occupation requiring special education (especially in the
       liberal arts or sciences)
    3: an open avowal (true or false) of some belief or opinion; "a
       profession of disagreement" [syn: profession, professing]
    4: affirmation of acceptance of some religion or faith; "a
       profession of Christianity"