a Scotch nobleman in the eleventh century, nearly allied to Duncan, king of Scotland. Not contented with curbing the king's authority, he carried his ambition so far as to put him to death; and, chasing Malcolm Canmore his son and heir into England, usurped the crown. But Siward, earl of Northumberland, whose daughter Duncan had married, undertook, by the order of Edward the Confessor, the protection of the fugitive prince; marched with an army into Scotland; defeated and killed Macbeth; and restored Malcolm Greathead to the throne of his ancestors. Shakspeare has made this transaction the subject of one of his best tragedies.