The Hebrew charam means to dedicate something irrevocably to God — either by destroying it (in the case of enemies) or by consecrating it so it cannot be reclaimed. The noun cherem (H2764) refers to the devoted thing itself.
Charam is one of the most theologically challenging concepts in the Old Testament — the 'ban' or 'holy war' dedication. When God commanded the destruction of Canaanite cities (Joshua 6:21), it was an act of cherem — complete consecration to God through total destruction, removing corruption from the covenant community. The tragic story of Achan (Joshua 7) shows the deadly seriousness of violating the cherem. The concept also had positive application: things devoted to God (Leviticus 27:28) could not be redeemed or sold. Charam forces the question of God's absolute sovereignty over what He creates and commands.