means The unlawful killing of a person without the premeditated intent that defines murder — death caused recklessly, in a heated moment, or through gross carelessness.

from A plain compound of two old English words: 'man' (a person) and 'slaughter,' which traces back to Old Norse 'slátr,' meaning butcher's meat or the killing of animals — a cousin of the verb 'slay.' So buried in the legal term is an uncomfortably literal image: a human being killed the way livestock is. The word has carried its grim sense since the medieval period, long before the careful legal line between murder and manslaughter was drawn.