The Collaborative International Dictionary of English v.0.48:

Dismission \Dis*mis"sion\, n. [Cf. L. dimissio.]
   1. The act dismissing or sending away; permission to leave;
      leave to depart; dismissal; as, the dismission of the
      grand jury.
      [1913 Webster]

   2. Removal from office or employment; discharge, either with
      honor or with disgrace.
      [1913 Webster]

   3. Rejection; a setting aside as trivial, invalid, or
      unworthy of consideration.
      [1913 Webster]

WordNet (r) 3.0 (2006):

dismission
    n 1: official notice that you have been fired from your job
         [syn: dismissal, dismission, pink slip]
    2: the termination of someone's employment (leaving them free to
       depart) [syn: dismissal, dismission, discharge,
       firing, liberation, release, sack, sacking]