Noun
reactive armour (countable and uncountable, plural reactive armours) (British spelling, Canadian spelling)
Vehicle armor which reacts to the impact of a weapon in such a way as to reduce the damage done, typically by exploding to disrupt the penetrating jet of a shaped-charge weapon.
Blazer explosive reactive armour (ERA) blocks on an Israeli M-60 Reactive armour consists of small explosive-filled metal boxes that detonate when hit by the metallic jet projected by an exploding HEAT warhead, causing their metal plates to disrupt it. Source: Internet
Reactive armours can also reduce the penetrative abilities of kinetic energy penetrators by deforming the penetrator with the metal plates on the Reactive armour, thereby reducing its effectiveness against the main armour of the tank. Source: Internet
Modern Reactive armour protects itself from Tandem warheads by having a thicker front metal plate to prevent the precursor charge from detonating the explosive in the reactive armour. Source: Internet