1. [n]  a cell for violent prisoners
2. [n]  a large (usually metallic) vessel for holding gases or liquids
3. [n]  an enclosed armored military vehicle; has a cannon and moves on caterpillar treads
4. [n]  a freight car that transports liquids or gases in bulk
5. [n]  as much as a tank will hold
6. [v]  treat in a tank; "tank animal refuse"
7. [v]  store in a tank by causing (something) to flow into it

Tank
Provides general information about tanks and specific facts about the features and operation of the M1A1 Abrams tank.

more details ...

1. \Tank\, n.
   A pond, pool, or small lake, natural or artificial.
         We stood in the afterglow on the bank of the tank and
         saw the ducks come homa.                 --F.
                                                  Remington.
         The tanks are full and the grass is high. --Lawson.
   

2. \Tank\, n.
   A small Indian dry measure, averaging 240 grains in weight;
   also, a Bombay weight of 72 grains, for pearls. --Simmonds.
   

3. \Tank\, n. [Pg. tanque, L. stangum a pool; or perhaps of
   East Indian origin. Cf. {Stank}, n.]
   A large basin or cistern; an artificial receptacle for
   liquids.
   {Tank engine}, a locomotive which carries the water and fuel
      it requires, thus dispensing with a tender.
   {Tank iron}, plate iron thinner than boiler plate, and
      thicker than sheet iron or stovepipe iron.
   {Tank worm} (Zo["o]l.), a small nematoid worm found in the
      water tanks of India, supposed by some to be the young of
      the Guinea worm.