The Collaborative International Dictionary of English v.0.48:

Suicide \Su"i*cide\, n. [L. sui of one's self (akin to suus
   one's own) + caedere to slay, to kill. Cf. So, adv.,
   Homicide.]
   1. The act of taking one's own life voluntary and
      intentionally; self-murder; specifically (Law), the
      felonious killing of one's self; the deliberate and
      intentional destruction of one's own life by a person of
      years of discretion and of sound mind.
      [1913 Webster]

   2. One guilty of self-murder; a felo-de-se.
      [1913 Webster]

   3. Ruin of one's own interests. "Intestine war, which may be
      justly called political suicide." --V. Knox.
      [1913 Webster]

WordNet (r) 3.0 (2006):

suicide
    n 1: the act of killing yourself; "it is a crime to commit
         suicide" [syn: suicide, self-destruction, self-
         annihilation]
    2: a person who kills himself intentionally [syn: suicide,
       felo-de-se]

Moby Thesaurus II by Grady Ward, 1.0:

32 Moby Thesaurus words for "suicide":
   aborticide, car of Jagannath, disembowelment, felo-de-se,
   fratricide, fungicide, genocide, germicide, hara-kiri, herbicide,
   homicide, infanticide, insecticide, mass suicide, matricide,
   microbicide, parricide, patricide, pesticide, regicide,
   ritual suicide, rodenticide, self-destruction, self-immolation,
   self-murder, self-sacrifice, seppuku, sororicide, suttee,
   sutteeism, uxoricide, vermicide



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

SUICIDE, crimes, med. jur. The act of malicious self-murder; felo de se.
(q.v.) 3 Man. Gran. & Scott, 437, 457, 458; 1 Hale, P. C.. 441. But it has
been decided in England that where a man's life was insured, and the policy
contained a proviso that "every policy effected by a person on his or her
own life should be void, if such person should commit suicide, or die by
duelling or the hands of justice," the terms of the condition included all
acts of voluntary self-destruction, whether the insured at the time such act
was committed, was or was not a moral responsible agent. 3 Man. Gr. & Scott,
437. In New York it has been held, that an insane person cannot commit
suicide, because. such person has no will. 4 Hill' 3 R. 75.
     2. It is not punishable it is believed in any of the United States, as
the unfortunate object of this offence is beyond the reach of human
tribunals, and to deprive his family of the property he leaves would be
unjust.
     3. In cases of sudden death, it is of great consequence to ascertain,
on finding the body, whether the deceased has been murdered, died suddenly
of a natural death, or whether he has committed suicide. By a careful
examination of the position of the body, and of the circumstances attending
it, it can be generally ascertained whether the deceased committed suicide,
was murdered, or died a natural death. But there are sometimes cases of
suicide which can scarcely be distinguished from those of murder. A case of
suicide is mentioned by Doctor Devergie, (Annales d'Hygiene, transcribed by
Trebuchet, Jurisprudence de la Medecine, p. 40,) which bears a striking
analogy to a murder. The individual went to the cemetery of Pere la Chaise,
near Paris, and with a razor inflicted a wound on himself immediately below
the oshyoide; the first blow penetrated eleven lines in depth; a second, in
the wound made by the first, pushed the instrument to the depth of twenty-
one lines; a third extended as far as the posterior of the pharynx, cutting
the muscles which attached the tongue to the oshyoide, and made a wound of
two inches in depth. Imagine an enormous wound, immediately under the chin,
two inches in depth, and three inches and three lines in width, and a foot
in circumference; and then judge whether such wound could not be easily
mistaken as having been made by a stranger, and not by the deceased. Vide
Death, and 1 Briand, Med. Leg. 2e partie, c. 1, art. 6.