A submunition is a munition that is dispensed from a larger piece of
ordnance, and not launched/dropped/fired by the human operator.
Cluster bombs dispense small submunitions which are in essence
antipersonnel grenades with a
shaped charge bottom for damaging vehicles and structures.
Submunitions can be intelligent. The American anti-armor weapon BAT dispenses small warheads with sensors. The usual reason for dispensing submunitions is to spread a lesser effect (than a unitary, straight high explosive payload) across a wider area. A Tomahawk cruise missile can be configured to dispense antipersonnel and anti-vehicle submunitions across an area large enough to contain parking for four to six jet aircraft, if imagery seen on the Discovery Channel can be believed.