Main Battle Tank
Usually abreviated to MBT.
Can be used to describe any type of tank whose main job is to kill other tanks and win the armour battle. They are big, they are clever and they have got a big feck-off gun.
The main UK MBTs of the past 50 years are:
Given the changes to the nature of warfare and the increasing cost of equipment it is unlikely that Challenger 2 will be replaced with anything resembling an MBT.