The Collaborative International Dictionary of English v.0.48:

wager \wa"ger\ (w[=a]"j[~e]r), n. [OE. wager, wajour, OF.
   wagiere, or wageure, F. gageure. See Wage, v. t.]
   [1913 Webster]
   1. Something deposited, laid, or hazarded on the event of a
      contest or an unsettled question; a bet; a stake; a
      pledge.
      [1913 Webster]

            Besides these plates for horse races, the wagers may
            be as the persons please.             --Sir W.
                                                  Temple.
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            If any atheist can stake his soul for a wager
            against such an inexhaustible disproportion, let him
            never hereafter accuse others of credulity.
                                                  --Bentley.
      [1913 Webster]

   2. (Law) A contract by which two parties or more agree that a
      certain sum of money, or other thing, shall be paid or
      delivered to one of them, on the happening or not
      happening of an uncertain event. --Bouvier.
      [1913 Webster]

   Note: At common law a wager is considered as a legal contract
         which the courts must enforce unless it be on a subject
         contrary to public policy, or immoral, or tending to
         the detriment of the public, or affecting the interest,
         feelings, or character of a third person. In many of
         the United States an action can not be sustained upon
         any wager or bet. --Chitty. --Bouvier.
         [1913 Webster]

   3. That on which bets are laid; the subject of a bet.
      [1913 Webster]

   Wager of battel, or Wager of battle (O. Eng. Law), the
      giving of gage, or pledge, for trying a cause by single
      combat, formerly allowed in military, criminal, and civil
      causes. In writs of right, where the trial was by
      champions, the tenant produced his champion, who, by
      throwing down his glove as a gage, thus waged, or
      stipulated, battle with the champion of the demandant,
      who, by taking up the glove, accepted the challenge. The
      wager of battel, which has been long in disuse, was
      abolished in England in 1819, by a statute passed in
      consequence of a defendant's having waged his battle in a
      case which arose about that period. See Battel.

   Wager of law (Law), the giving of gage, or sureties, by a
      defendant in an action of debt, that at a certain day
      assigned he would take a law, or oath, in open court, that
      he did not owe the debt, and at the same time bring with
      him eleven neighbors (called compurgators), who should
      avow upon their oaths that they believed in their
      consciences that he spoke the truth.

   Wager policy. (Insurance Law) See under Policy.

   Wagering contract or gambling contract. A contract which
      is of the nature of wager. Contracts of this nature
      include various common forms of valid commercial
      contracts, as contracts of insurance, contracts dealing in
      futures, options, etc. Other wagering contracts and bets
      are now generally made illegal by statute against betting
      and gambling, and wagering has in many cases been made a
      criminal offence. [Webster 1913 Suppl.]
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

wager \wa"ger\, v. t. [imp. & p. p. wagered (w[=a]"j[~e]rd);
   p. pr. & vb. n. wagering.]
   To hazard on the issue of a contest, or on some question that
   is to be decided, or on some eventuality; to lay; to stake;
   to bet.
   [1913 Webster]

         And wagered with him
         Pieces of gold 'gainst this which he wore. --Shak.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Wager \Wa"ger\, v. i.
   To make a bet; to lay a wager.
   [1913 Webster]

         'T was merry when
         You wagered on your angling.             --Shak.
   [1913 Webster]

WordNet (r) 3.0 (2006):

wager
    n 1: the act of gambling; "he did it on a bet" [syn: bet,
         wager]
    2: the money risked on a gamble [syn: stake, stakes, bet,
       wager]
    v 1: stake on the outcome of an issue; "I bet $100 on that new
         horse"; "She played all her money on the dark horse" [syn:
         bet, wager, play]
    2: maintain with or as if with a bet; "I bet she will be there!"
       [syn: bet, wager]

Moby Thesaurus II by Grady Ward, 1.0:

60 Moby Thesaurus words for "wager":
   adventure, ante, ante up, back, bet, bet on, blind bargain, book,
   borderline case, call, chance, chance it, chunk, contingency,
   cover, double contingency, fade, gamble, gamble on, game, guess,
   handbook, hazard, lay, lay a wager, lay down, make a bet,
   meet a bet, open question, parlay, pass, piece of guesswork, play,
   play against, plunge, pot, punt, put on, question, rely on fortune,
   risk, run a chance, run the risk, see, set, set at hazard, shot,
   sight-unseen transaction, stake, stand pat, take a chance,
   take a flier, take chances, tempt fortune, toss-up, touch and go,
   trust to chance, try the chance, undecided issue, venture



Bouvier's Law Dictionary, Revised 6th Ed (1856):

WAGERS. A wager is a bet a contract by which two parties or more agree that
a certain sum of money, or other thing, shall be paid or delivered to one of
them, on the happening or not happening of an uncertain event.
     2. The law does not prohibit all wagers. 1 Browne's Rep. 171 Poth. du
Jeu, n. 4.
     3. To restrain wagers within the bounds of justice the following
conditions must be observed: 1. Each of the parties must have the right to
dispose of the thing which is the object of the wager. 2. Each must give a
perfect and full consent to the contract, 3. There must he equality between
the parties. 4. There must be good faith between them. 5. The wager must not
be forbidden by law. Poth. du
     4. In general, it seems that a wager is legal and maybe enforced in a
court of law 3 T. R. 693, if it be not, 1st, Contrary to public policy, or
immoral; or if it do not in some other respect tend to the detriment of the
public. 2d. If it do not affect the interest, feelings, or character of a
third person.
     5.-1. Wagers on the event of an election laid before the poll is open;
1 T. R. 56. 4 Johns. 426; 4 Harr. & McH. 284; or after it is closed; 8
Johns. 454, 147; 2 Browne's Rep. 182; are unlawful. And wagers are against
public policy if they are in restraint of marriage; 10 East, R. 22; made as
to the mode of playing an illegal game; 2 H. Bl. 43; 1 Nott & McCord, 180; 7
Taunt. 246; or on an abstract speculative question of law or judicial
practice, not arising out of circumstances in which the parties have a real
interest. 12 East, R. 247, and Day's notes, sed vide Cowp. 37.
     6.-2. Wagers as to the sex of an individual Cowp. 729; or whether an
unmarried woman had borne or would have a child; 4 Campb. 152, are illegal;
as unnecessarily leading to painful and indecent considerations. The supreme
court of Pennsylvania have laid it down as a rule, that every bet about the
age, or height, or weight, or wealth, or circumstances, or situation of any
person, is illegal; and this whether the subject of the bet be man, woman,
or child, married or single, native or foreigner, in this country or abroad.
1 Rawle, 42. And it seems that a wager between two coach-proprietors,
whether or not a particular person would go by one of their coaches is
illegal, as exposing that person to inconvenience. 1 B. & A. 683.
     7. In the case even of a legal wager, the authority of a stakeholder,
like that of an arbitrator, may be rescinded by either party before the
event happens. And if after his authority has been countermanded, and the
stake has been demanded, he refuse to deliver it, trover or assumpsit for
money had and received is maintainable. 1 B. & A. 683. And where the wager
is in its nature illegal, the stake may be recovered, even after the event,
on demand made before it has been paid over. 4 Taunt. 474; 5 T. R. 405; sed
vide 12 Johns. 1. See further on this subject, 7 Johns. 434; 11 Johns. 23;
10 Johns. 406,468; 12 Johns. 376; 17 Johns. 192; 15 Johns. 5; 13 Johns. 88;
Mann. Dig. Gaming; Harr. Dig. Gaining; Stakeholder.