The Collaborative International Dictionary of English v.0.48:

Ordeal \Or"de*al\ ([^o]r"d[-e]*al), n. [AS. ord[=a]l, ord[=ae]l,
   a judgment; akin to D. oordeel, G. urteil, urtheil; orig.,
   what is dealt out, the prefix or- being akin to [=a]-
   compounded with verbs, G. er-, ur-, Goth. us-, orig. meaning,
   out. See Deal, v. & n., and cf. Arise, Ort.]
   1. An ancient form of test to determine guilt or innocence,
      by appealing to a supernatural decision, -- once common in
      Europe, and still practiced in the East and by savage
      tribes.
      [1913 Webster]

   Note: In England ordeal by fire and ordeal by water were
         used, the former confined to persons of rank, the
         latter to the common people. The ordeal by fire was
         performed, either by handling red-hot iron, or by
         walking barefoot and blindfold over red-hot plowshares,
         laid at unequal distances. If the person escaped
         unhurt, he was adjudged innocent; otherwise he was
         condemned as guilty. The ordeal by water was performed,
         either by plunging the bare arm to the elbow in boiling
         water, an escape from injury being taken as proof of
         innocence, or by casting the accused person, bound hand
         and foot, into a river or pond, when if he floated it
         was an evidence of guilt, but if he sunk he was
         acquitted. It is probable that the proverbial phrase,
         to go through fire and water, denoting severe trial or
         danger, is derived from the ordeal. See Wager of
         battle, under Wager.
         [1913 Webster]

   2. Any severe trial, or test; a painful experience.
      [1913 Webster]

   Ordeal bean. (Bot.) See Calabar bean, under Calabar.

   Ordeal root (Bot.) the root of a species of Strychnos
      growing in West Africa, used, like the ordeal bean, in
      trials for witchcraft.

   Ordeal tree (Bot.), a poisonous tree of Madagascar
      (Tanghinia venenata syn. Cerbera venenata). Persons
      suspected of crime are forced to eat the seeds of the
      plumlike fruit, and criminals are put to death by being
      pricked with a lance dipped in the juice of the seeds.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Ordeal \Or"de*al\, a.
   Of or pertaining to trial by ordeal.
   [1913 Webster]

WordNet (r) 3.0 (2006):

ordeal
    n 1: a severe or trying experience
    2: a primitive method of determining a person's guilt or
       innocence by subjecting the accused person to dangerous or
       painful tests believed to be under divine control; escape was
       usually taken as a sign of innocence [syn: ordeal, trial
       by ordeal]

Moby Thesaurus II by Grady Ward, 1.0:

49 Moby Thesaurus words for "ordeal":
   Sabbat, acid test, adversity, affliction, anguish, assay,
   blank determination, brouillon, calvary, criterion, cross,
   crucial test, crucible, determination, disaster, distress,
   docimasy, essay, feeling out, fiery ordeal, first draft,
   ghost dance, grief, hardship, kiteflying, magic circle, misery,
   misfortune, nightmare, ordeal by battle, probation, proof,
   rough draft, rough sketch, sounding out, standard, suffering, test,
   test case, touchstone, tragedy, trial, trials and tribulations,
   tribulation, tribulations, troubles, try, verification,
   visitation



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

ORDEAL. An ancient superstitious mode of tribal. When in a criminal case the
accused was arraigned, be might select the mode of trial either by God and
his country, that is, by jury; or by God only, that is by ordeal.
     2. The trial by ordeal was either by fire or by water. Those who were
tried by the former passed barefooted and blindfolded over nine hot glowing
ploughshares; or were to carry burning irons in their hands; and accordingly
as they escaped or not, they were acquitted or condemned. The water ordeal
was performed either in hot or cold water. In cold water, the parties
suspected were adjudged innocent, if their bodies were not borne up by the
water contrary to the course of nature; and if, after putting their bare
arms or legs into scalding water they came out unhurt, they were taken to be
innocent of the crime.
     3. It was impiously supposed that God would, by the mere contrivance of
man, exercise his power in favor of the innocent. 4. Bl. Com. 342; 2 Am.
Jur. 280. For a detailed account of the trial by ordeal, see Herb. Antiq. of
the Inns of Court, 146.