manslaughter [(man-slaw-tuhr)] The unlawful killing of a person, without malice or premeditation. Involuntary manslaughter is accidental, such as running into someone with a car. Voluntary manslaughter is committed in the “heat of passion,” as in a spontaneous fight in which one person is killed by a strong blow. Manslaughter is usually considered less serious than murder. Both murder and manslaughter are types of homicide.