The Collaborative International Dictionary of English v.0.48:

Guillotine \Guil"lo*tine`\ (g[i^]l`l[-o]*t[=e]n"), v. t. [imp. &
   p. p. Guillotined; p. pr. & vb. n. Guillotining.] [Cf. F.
   guillotiner.]
   To behead with the guillotine.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Guillotine \Guil"lo*tine`\ (g[i^]l"l[-o]*t[=e]n`), n. [F., from
   Guillotin, a French physician, who proposed, in the
   Constituent Assembly of 1789, to abolish decapitation with
   the ax or sword. The instrument was invented by Dr. Antoine
   Louis, and was called at first Louison or Louisette.
   Similar machines, however, were known earlier.]
   1. A machine for beheading a person by one stroke of a heavy
      ax or blade, which slides in vertical guides, is raised by
      a cord, and let fall upon the neck of the victim.
      [1913 Webster]

   2. Any machine or instrument for cutting or shearing,
      resembling in its action a guillotine.
      [1913 Webster]

WordNet (r) 3.0 (2006):

guillotine
    n 1: closure imposed on the debate of specific sections of a
         bill [syn: closure by compartment, guillotine]
    2: instrument of execution that consists of a weighted blade
       between two vertical poles; used for beheading people
    v 1: kill by cutting the head off with a guillotine; "The French
         guillotined many Vietnamese while they occupied the
         country"

Moby Thesaurus II by Grady Ward, 1.0:

72 Moby Thesaurus words for "guillotine":
   ax, behead, beheading, block, bowstring, burn, burning,
   capital punishment, cloture, cloture by compartment, cross,
   crucifixion, crucify, death chair, death chamber, decapitate,
   decapitation, decollate, decollation, defenestrate, defenestration,
   drop, electric chair, electrocute, electrocution, execute,
   execution, fusillade, gallows, gallows-tree, garrote, gas chamber,
   gassing, gibbet, halter, hanging, head, hemlock, hemp,
   hempen collar, hot seat, inflict capital punishment,
   judicial murder, kangaroo cloture, lapidate, lapidation,
   lethal chamber, maiden, necktie party, noose, poisoning,
   put to death, rope, scaffold, shoot, shooting, stake, stem, stone,
   stoning, strangle, strangling, strangulation, the ax, the block,
   the chair, the gallows, the gas chamber, the guillotine,
   the hot seat, the rope, tree



The Devil's Dictionary (1881-1906):

GUILLOTINE, n.  A machine which makes a Frenchman shrug his shoulders
with good reason.
    In his great work on _Divergent Lines of Racial Evolution_, the
learned Professor Brayfugle argues from the prevalence of this gesture
-- the shrug -- among Frenchmen, that they are descended from turtles
and it is simply a survival of the habit of retracing the head inside
the shell.  It is with reluctance that I differ with so eminent an
authority, but in my judgment (as more elaborately set forth and
enforced in my work entitled _Hereditary Emotions_ -- lib. II, c. XI)
the shrug is a poor foundation upon which to build so important a
theory, for previously to the Revolution the gesture was unknown.  I
have not a doubt that it is directly referable to the terror inspired
by the guillotine during the period of that instrument's activity.