The Collaborative International Dictionary of English v.0.48:

foregone conclusion \foregone conclusion\ n.
   An inevitable outcome; a certain result; a certainty.
   [PJC]

The Collaborative International Dictionary of English v.0.48:

Forego \Fore*go"\, v. t. [AS. foreg[=a]n; fore + g[=a]n to go;
   akin to G. vorgehen to go before, precede. See Go, v. i.]
   To go before; to precede; -- used especially in the present
   and past participles.
   [1913 Webster]

         Pleasing remembrance of a thought foregone.
                                                  --Wordsworth.
   [1913 Webster]

         For which the very mother's face forewent
         The mother's special patience.           --Mrs.
                                                  Browning.
   [1913 Webster]

   Foregone conclusion, a conclusion which has preceded
      argument or examination; a predetermined conclusion.
      [1913 Webster]

WordNet (r) 3.0 (2006):

foregone conclusion
    n 1: an inevitable ending [syn: foregone conclusion, matter
         of course]
    2: something that is certain; "his victory is a certainty" [syn:
       certainty, sure thing, foregone conclusion] [ant:
       precariousness, uncertainness, uncertainty]