neonaticide Share definition Flag The act of killing a newborn within twenty-four hours of its life. Though rare, it is more common among mothers than fathers. Though the morality of abortion is debated, one cannot argue that neonaticide is murder. neonaticide by PrincessZeffie April 10, 2009 0 0 Get merch Get the neonaticide mug. Buy Now — $32.95 See more merch