Source : Webster's Revised Unabridged Dictionary (1913)

Manslaughter \Man"slaugh`ter\, n.
   1. The slaying of a human being; destruction of men.
      --Milton.

   2. (Law) The unlawful killing of a man, either in negligenc?
      or incidentally to the commission of some unlawful act,
      but without specific malice, or upon a sudden excitement
      of anger.

Source : WordNet®

manslaughter
     n : homicide without malice aforethought