2) The modern equivalent of a siege engine.
2) Someone who is strong and/or physically imposing.
3) In roleplaying games, a melee damage-dealer (or to act as one).
2) My brother drives a tank in the army.
3) Is your sister still dating that tank of a football player?
4) LF tank for ZF run.
Verb: To "tank", or "tanking", would be the action of performing the duties of the tank as described above.
2.V. The warrior is tanking the mob right now.
3.V. Do you think you can tank this mob for us?