armour. n. 1. (Arms & Armour (excluding Firearms)) any defensive covering, esp that of metal, chain mail, etc, worn by medieval warriors to prevent injury to the body in battle. 2. (Arms & Armour (excluding Firearms)) the protective metal plates on a tank, warship, etc.rmour-protective covering made of metal and used in combat. armor. body armor, body armour, cataphract, coat of mail, suit of armor, suit of armour-armor that protects the wearer's whole body.