2. Verb: Doing something exceptionally well.
3. Adjective: Possessing the trait of being extremely good at something.
4. Noun: One who is generally awesome.
2. Michael Phelps is tanking it up in the pool!
3. Usain Bolt is tanktastic!
4. Ryan Lochte is a straight up tank.
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?