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]