Source : Webster's Revised Unabridged Dictionary (1913)

Tank \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.

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

Tank \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.

Source : WordNet®

tank
     v 1: store in a tank by causing (something) to flow into it
     2: treat in a tank; "tank animal refuse"

tank
     n 1: an enclosed armored military vehicle; has a cannon and moves
          on caterpillar treads [syn: {army tank}, {armored combat
          vehicle}, {armoured combat vehicle}]
     2: a large (usually metallic) vessel for holding gases or
        liquids [syn: {storage tank}]
     3: as much as a tank will hold [syn: {tankful}]
     4: a freight car that transports liquids or gases in bulk [syn:
         {tank car}]
     5: a cell for violent prisoners [syn: {cooler}]