What is the X in X-mas?
"the killing of another person," early 13c., from Old French homicide, from Latin homicidium "manslaughter," from homo "man" (see homunculus) + -cidium "act of killing" (see -cide). The meaning "person who kills another" (late 14c.) also is from French, from Latin homicida "a murderer," from -cida "killer."
The killing of one person by another, whether intended (murder) or not (manslaughter). Not all homicide is unlawful; killing in self-defense, for example, is not a crime.