Source : Webster's Revised Unabridged Dictionary (1913)

Occurrence \Oc*cur"rence\, n. [Cf. F. occurrence. See {Occur}.]
   1. A coming or happening; as, the occurence of a railway
      collision.

            Voyages detain the mind by the perpetual occurrence
            and expectation of something new.     --I. Watts.

   2. Any incident or event; esp., one which happens without
      being designed or expected; as, an unusual occurrence, or
      the ordinary occurrences of life.

            All the occurrence of my fortune.     --Shak.

   Syn: See {Event}.

Source : WordNet®

occurrence
     n 1: an event that happens [syn: {happening}, {natural event}]
     2: an instance of something occurring; "a disease of frequent
        occurrence"; "the occurrence (or presence) of life on
        other planets"