noun

• (Australia, India) A reservoir or dam.
• (botany) A structure of tightly overlapping leaves used by some bromeliads to retain water.
• (colloquial) A very muscular and physically imposing person; somebody who is built like a tank.
• (UK, slang, dated, by extension) A bouncer or doorman.

verb

• (video games) To attract the attacks of an enemy target in cooperative team-based combat, so that one's teammates can defeat the enemy in question more efficiently.
• (transitive) To put (fuel, etc.) into a tank.
  "Concrete below ground must be fully tanked to prevent water uptake."
• (fandom slang) To resist damage; to be attacked without being hurt.
  "Unless Bane can tank Helicarrier-busting explosions I'm not sure how he stands a chance."
• (originally poker, slang) To contemplate a decision for a long time; to go in the tank.