The Collaborative International Dictionary of English v.0.48:

Likelihood \Like"li*hood\ (l[imac]k"l[i^]*h[oo^]d), n. [Likely +
   -hood.]
   1. Appearance; show; sign; expression. [Obs.]
      [1913 Webster]

            What of his heart perceive you in his face
            By any likelihood he showed to-day ?  --Shak.
      [1913 Webster]

   2. Likeness; resemblance. [Obs.]
      [1913 Webster]

            There is no likelihood between pure light and black
            darkness, or between righteousness and reprobation.
                                                  --Sir W.
                                                  Raleigh.
      [1913 Webster]

   3. Appearance of truth or reality; probability;
      verisimilitude. --Tennyson.
      [1913 Webster]

   4. Statistical probability; probability of being true or of
      occurring in the future; as, the likelihood of being
      abducted by aliens is close to zero..
      [PJC]

WordNet (r) 3.0 (2006):

likelihood
    n 1: the probability of a specified outcome [syn: likelihood,
         likeliness] [ant: unlikelihood, unlikeliness]