Wiktionary
n. A large ballistic projectile, with a propellent charge, typically used for riot control.
WordNet
n. a bullet made of hard rubber; designed for use in crowd control
Wikipedia
Rubber bullets (also called rubber baton rounds) are rubber or rubber-coated projectiles that can be fired from either standard firearms or dedicated riot guns. They are intended to be a non-lethal alternative to metal projectiles. Like other similar projectiles made from plastic, wax, and wood, rubber bullets may be used for short range practice and animal control, but are most commonly associated with use in riot control and to disperse protests. These types of projectiles are sometimes called baton rounds. Rubber projectiles have largely been replaced by other materials as rubber tends to bounce uncontrollably.
Such "kinetic impact munitions" are meant to cause pain but not serious injury. They are expected to produce contusions, abrasions, and hematomas. However, they may cause bone fractures, injuries to internal organs, or death. In a study of injuries in 90 patients injured by rubber bullets, one died, 17 suffered permanent disabilities or deformities and 41 required hospital treatment after being fired upon with rubber bullets.
Rubber bullets were invented by the British Ministry of Defence for use against rioters in Northern Ireland during The Troubles, and were first used there in 1970.
Usage examples of "rubber bullet".
A rubber bullet, solid, unbending, six inches long, was fired into the crowd, and amid the screams there was a stampede away from the troops as tables and chairs were thrown aside to make way.
His arm was permanently scarred from an Israeli club, and half his teeth were gone from a rubber bullet whose shooter had been especially angry on one particular day.
If they made a mistake and an alarm were sounded, every guard exiting a burre around the main garden, or for that matter the main house, would take a rubber bullet to the chest from a silenced rifle.