The Collaborative International Dictionary of English v.0.48:

Crucifixion \Cru`ci*fix"ion\ (kr?`s?-f?k"sh?n), n.
   1. The act of nailing or fastening a person to a cross, for
      the purpose of putting him to death; the use of the cross
      as a method of capital punishment.
      [1913 Webster]

   2. The state of one who is nailed or fastened to a cross;
      death upon a cross.
      [1913 Webster]

   3. Intense suffering or affliction; painful trial.
      [1913 Webster]

            Do ye prove
            What crucifixions are in love?        --Herrick.
      [1913 Webster]

WordNet (r) 3.0 (2006):

crucifixion
    n 1: the act of executing by a method widespread in the ancient
         world; the victim's hands and feet are bound or nailed to a
         cross
    2: the death of Jesus by crucifixion
    3: the infliction of extremely painful punishment or suffering
       [syn: crucifixion, excruciation]

Moby Thesaurus II by Grady Ward, 1.0:

50 Moby Thesaurus words for "crucifixion":
   agony, anguish, atrocious pain, beheading, burning,
   capital punishment, clawing, cruciation, decapitation, decollation,
   defenestration, electrocution, excruciation, execution, fusillade,
   garrote, gassing, hanging, hell, hell upon earth, hemlock,
   holocaust, horror, judicial murder, laceration, lancination,
   lapidation, martyrdom, martyrization, necktie party, nightmare,
   passion, persecution, poisoning, purgatory, rack, shooting,
   stoning, strangling, strangulation, the ax, the block, the chair,
   the gallows, the gas chamber, the guillotine, the hot seat,
   the rope, torment, torture



Easton's 1897 Bible Dictionary:

Crucifixion
   a common mode of punishment among heathen nations in early
   times. It is not certain whether it was known among the ancient
   Jews; probably it was not. The modes of capital punishment
   according to the Mosaic law were, by the sword (Ex. 21),
   strangling, fire (Lev. 20), and stoning (Deut. 21).

     This was regarded as the most horrible form of death, and to a
   Jew it would acquire greater horror from the curse in Deut.
   21:23.

     This punishment began by subjecting the sufferer to scourging.
   In the case of our Lord, however, his scourging was rather
   before the sentence was passed upon him, and was inflicted by
   Pilate for the purpose, probably, of exciting pity and procuring
   his escape from further punishment (Luke 23:22; John 19:1).

     The condemned one carried his own cross to the place of
   execution, which was outside the city, in some conspicuous place
   set apart for the purpose. Before the nailing to the cross took
   place, a medicated cup of vinegar mixed with gall and myrrh (the
   sopor) was given, for the purpose of deadening the pangs of the
   sufferer. Our Lord refused this cup, that his senses might be
   clear (Matt. 27:34). The spongeful of vinegar, sour wine, posca,
   the common drink of the Roman soldiers, which was put on a
   hyssop stalk and offered to our Lord in contemptuous pity (Matt.
   27:48; Luke 23:36), he tasted to allay the agonies of his thirst
   (John 19:29). The accounts given of the crucifixion of our Lord
   are in entire agreement with the customs and practices of the
   Roman in such cases. He was crucified between two "malefactors"
   (Isa. 53:12; Luke 23:32), and was watched by a party of four
   soldiers (John 19:23; Matt. 27:36, 54), with their centurion.
   The "breaking of the legs" of the malefactors was intended to
   hasten death, and put them out of misery (John 19:31); but the
   unusual rapidity of our Lord's death (19:33) was due to his
   previous sufferings and his great mental anguish. The omission
   of the breaking of his legs was the fulfilment of a type (Ex.
   12:46). He literally died of a broken heart, a ruptured heart,
   and hence the flowing of blood and water from the wound made by
   the soldier's spear (John 19:34). Our Lord uttered seven
   memorable words from the cross, namely, (1) Luke 23:34; (2)
   23:43; (3) John 19:26; (4) Matt. 27:46, Mark 15:34; (5) John
   19:28; (6) 19:30; (7) Luke 23:46.