Definition from Wiktionary, the free dictionary
familicide (plural familicides)
- The murder of an entire family by a family member.
- Because of the familicide that wiped out his entire family, he will be charged with six counts of murder.
- The murder of an entire family by a family member, followed by suicide.
- His spree of familicide ended only after he killed the family dog, and then himself.
- The person who perpetrates a familicide.
- The popular professional wrestler became the most notorious familicide of 2007.
Derived terms 
- Familicide: The killing of spouse and children, Margo Wilson, et al., in Aggressive Behavior (psychology journal), Vol. 21:4, pp. 275 - 291, February 13, 2006:
- A familicide is a multiple-victim homicide incident in which the killer's spouse and one or more children are slain.... Familicides were almost exclusively perpetrated by men, unlike other spouse-killings and other filicides. Half the familicidal men killed themselves as well, a much higher rate of suicide than among other uxoricidal or filicidal men.
- Behind dad's slaying of family, San Francisco Chronicle, June 20, 2007:
- Investigators say Kevin Morrissey, 51, was overwhelmed by money problems when he parked his car in Tilden Park and killed his two children, his wife and then himself Monday evening. Experts on "familicide" -- the term used by psychologists and criminologists to describe the killing of one's entire family and oneself -- said Morrissey fit the profile.