The Collaborative International Dictionary of English v.0.48:

Felo-de-se \Fe"lo-de-se`\, n.; pl. Felos-de-se. [LL. felo, E.
   felon + de of, concerning + se self.] (Law)
   One who deliberately puts an end to his own existence, or
   loses his life while engaged in the commission of an unlawful
   or malicious act; a suicide. --Burrill.
   [1913 Webster]

WordNet (r) 3.0 (2006):

felo-de-se
    n 1: a person who kills himself intentionally [syn: suicide,
         felo-de-se]
    2: an act of deliberate self destruction