ETYM Old Eng. morder, morther, as. morthor, from morth murder.
Unlawful premeditated killing of a human being; SYN. homicide, slaying.
Unlawful killing of one person by another. In the us, first-degree murder requires proof of premeditation; second-degree murder falls between first-degree murder and manslaughter.
If the killer can show provocation by the victim (action or words that would make a reasonable person lose self-control) or diminished responsibility (an abnormal state of mind caused by illness, injury, or mental subnormality), the charge may be reduced to a less serious one. See also assassination and homicide.

To kill intentionally and with premeditation; SYN. slay, hit, dispatch, bump off, polish off, remove.