The Collaborative International Dictionary of English v.0.48:

Odds \Odds\ ([o^]dz), n. sing. & pl. [See Odd, a.]
   1. Difference in favor of one and against another; excess of
      one of two things or numbers over the other; inequality;
      advantage; superiority; hence, excess of chances;
      probability. The odds are often expressed by a ratio; as,
      the odds are three to one that he will win, i. e. he will
      win three times out of four "Preeminent by so much odds."
      --Milton. "The fearful odds of that unequal fray."
      --Trench.
      [1913 Webster]

            The odds
            Is that we scarce are men and you are gods. --Shak.
      [1913 Webster]

            There appeared, at least, four to one odds against
            them.                                 --Swift.
      [1913 Webster]

            All the odds between them has been the different
            scope . . . given to their understandings to range
            in.                                   --Locke.
      [1913 Webster]

            Judging is balancing an account and determining on
            which side the odds lie.              --Locke.
      [1913 Webster]

   2. Quarrel; dispute; debate; strife; -- chiefly in the phrase
      at odds.
      [1913 Webster]

            Set them into confounding odds.       --Shak.
      [1913 Webster]

            I can not speak
            Any beginning to this peevish odds.   --Shak.
      [1913 Webster]

   At odds, in dispute; at variance. "These squires at odds
      did fall." --Spenser. "He flashes into one gross crime or
      other, that sets us all at odds." --Shak.

   It is odds, it is probable; same as odds are, but no
      longer used. [Obs.] --Jer. Taylor.

   odds are it is probable; as, odds are he will win the gold
      medal.

   Odds and ends, that which is left; remnants; fragments;
      refuse; scraps; miscellaneous articles. "My brain is
      filled . . . with all kinds of odds and ends." --W.
      Irving.

   slim odds low odds; poor chances; as, there are slim odds
      he will win any medal.
      [1913 Webster +PJC]

WordNet (r) 3.0 (2006):

odds
    n 1: the likelihood of a thing occurring rather than not
         occurring
    2: the ratio by which one better's wager is greater than that of
       another; "he offered odds of two to one" [syn: odds,
       betting odds]

Moby Thesaurus II by Grady Ward, 1.0:

154 Moby Thesaurus words for "odds":
   advantage, agreement to disagree, allowance, aptitude, asymmetry,
   at daggers drawn, at loggerheads, at odds, at variance, bulge,
   chance, chances, clashing, coign of vantage, conflicting,
   contrariety, contrast, cross-purposes, deadwood, debris, departure,
   deviation, difference, difference of opinion, differing,
   difficulty, disaccord, disaccordance, disagreeing, disagreement,
   disconformity, discongruity, discordance, discrepancy,
   discreteness, disequilibrium, disparity, disproportion, dissent,
   dissimilarity, dissonance, distinction, distinctness, divergence,
   divergency, diversity, dividedness, division, draw, drop, edge,
   equivalent odds, even break, even chance, expectation,
   fair expectation, fair shake, far cry, favorable prospect,
   fifty-fifty, flying start, fragments, good chance, half a chance,
   handicap, head start, heterogeneity, hundred-to-one shot,
   imbalance, in disagreement, in opposition, inaccordance,
   inadequacy, incompatibility, incongruity, inconsistency,
   inconsonance, inequality, inequity, inharmonious, inharmoniousness,
   inharmony, injustice, inside track, insufficiency,
   irreconcilability, irregularity, jump, lead, leavings, leftovers,
   liability, likelihood, likeliness, litter, long odds, long shot,
   misunderstanding, mixture, no chance, nonconformity, nonuniformity,
   oddments, odds and ends, opposition, otherness, out of line,
   outlook, overbalance, particles, polarization, presumption,
   presumptive evidence, price, probabilism, probability, prospect,
   reasonable ground, reasonable hope, rubbish, running start, scraps,
   separateness, short odds, shortcoming, shreds, small chance,
   something extra, something in reserve, square odds, standoff,
   start, superiority, tendency, toss, toss-up, touch and go,
   unbalance, unconformity, unevenness, unfair discrimination,
   unlikeness, unorthodoxy, upper hand, vantage, vantage ground,
   vantage point, variance, variation, variegation, variety,
   verisimilitude, well-grounded hope, whip hand