1. The secret killing of someone.
2. A fine against the tithing where the secret and unsolved homicide took place.
“The readiness with which the Norman administrators seized on this Anglo-Saxon system was probably due to its effectiveness in collecting the murdrum, the murder fine. In ordinary cases of homicide, the whole district — except the kin of the suspect — would be zealous to bring the malefactor to justice. But we can readily see that, if the person killed was a Norman, every effort would be made to shield the murderer. The Norman rulers had recourse to the device … of imposing a group responsibility. The tithing within which the murdered Norman was found was compelled to pay a fine or to discover and surrender the homicide. The word murdrum is a word of uncertain etymology, and has given us our term for willful homicide.” Max Radin, Handbook of Anglo-American Legal History 175–76 (1936).
3. Murder; specif., murder with malice aforethought. See MALICE AFORETHOUGHT.