MBT is the common abbreviation for the term 'Main Battle Tank'. A Main Battle Tank is the type of Armoured Fighting Vehicle which is distinguished from other types in having the most armour mounted on any armored vehicle type, and the most powerful direct-fire gun which is mounted on any vehicle type.
The term MBT, or main battle tank is used to distinguish the most powerful and most modern type of tank in any army from lighter, less costly tanks which are sometimes used for airborne or amphibious operations, or from older tanks which are used in secondary roles.