The Collaborative International Dictionary of English v.0.48:

Vocation \Vo*ca"tion\ (v[-o]*k[=a]"sh[u^]n), n. [L. vocatio a
   bidding, invitation, fr. vocare to call, fr. vox, vocis,
   voice: cf. F. vocation. See Vocal.]
   1. A call; a summons; a citation; especially, a designation
      or appointment to a particular state, business, or
      profession.
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            What can be urged for them who not having the
            vocation of poverty to scribble, out of mere
            wantonness make themselves ridiculous? --Dryden.
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   2. Destined or appropriate employment; calling; occupation;
      trade; business; profession.
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            He would think his service greatly rewarded, if he
            might obtain by that means to live in the sight of
            his prince, and yet practice his own chosen
            vocation.                             --Sir. P.
                                                  Sidney.
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   3. (Theol.) A calling by the will of God. Specifically:
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      (a) The bestowment of God's distinguishing grace upon a
          person or nation, by which that person or nation is
          put in the way of salvation; as, the vocation of the
          Jews under the old dispensation, and of the Gentiles
          under the gospel. "The golden chain of vocation,
          election, and justification." --Jer. Taylor.
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      (b) A call to special religious work, as to the ministry.
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                Every member of the same [the Church], in his
                vocation and ministry.            --Bk. of Com.
                                                  Prayer.
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WordNet (r) 3.0 (2006):

vocation
    n 1: the particular occupation for which you are trained [syn:
         career, calling, vocation]
    2: a body of people doing the same kind of work [syn:
       occupational group, vocation]