The unlawful killing of a human being with deliberate intent to kill: (1) murder in the first degree is characterized by premeditation; (2) murder in the second degree is characterized by a sudden and instantaneous intent to kill or to cause injury without caring whether the injury kills or not.

Source: U.S. Courts

The unlawful killing of a person by another with premeditated malice, either expressed (said) or implied (suggested). (See also homicide; compare with manslaughter.)

Source: California Courts.