Source : Webster's Revised Unabridged Dictionary (1913)

Well \Well\, n. [OE. welle, AS. wella, wylla, from weallan to
   well up, surge, boil; akin to D. wel a spring or fountain.
   ????. See {Well}, v. i.]
   1. An issue of water from the earth; a spring; a fountain.

            Begin, then, sisters of the sacred well. --Milton.

   2. A pit or hole sunk into the earth to such a depth as to
      reach a supply of water, generally of a cylindrical form,
      and often walled with stone or bricks to prevent the earth
      from caving in.

            The woman said unto him, Sir, thou hast nothing to
            draw with, and the well is deep.      --John iv. 11.

   3. A shaft made in the earth to obtain oil or brine.

   4. Fig.: A source of supply; fountain; wellspring. ``This
      well of mercy.'' --Chaucer.

            Dan Chaucer, well of English undefiled. --Spenser.

            A well of serious thought and pure.   --Keble.

   5. (Naut.)
      (a) An inclosure in the middle of a vessel's hold, around
          the pumps, from the bottom to the lower deck, to
          preserve the pumps from damage and facilitate their
          inspection.
      (b) A compartment in the middle of the hold of a fishing
          vessel, made tight at the sides, but having holes
          perforated in the bottom to let in water for the
          preservation of fish alive while they are transported
          to market.
      (c) A vertical passage in the stern into which an
          auxiliary screw propeller may be drawn up out of
          water.
      (d) A depressed space in the after part of the deck; --
          often called the cockpit.

   6. (Mil.) A hole or excavation in the earth, in mining, from
      which run branches or galleries.

   7. (Arch.) An opening through the floors of a building, as
      for a staircase or an elevator; a wellhole.

   8. (Metal.) The lower part of a furnace, into which the metal
      falls.

   {Artesian well}, {Driven well}. See under {Artesian}, and
      {Driven}.

   {Pump well}. (Naut.) See {Well}, 5
      (a), above.

   {Well boring}, the art or process of boring an artesian well.
      

   {Well drain}.
      (a) A drain or vent for water, somewhat like a well or
          pit, serving to discharge the water of wet land.
      (b) A drain conducting to a well or pit.

   {Well room}.
      (a) A room where a well or spring is situated; especially,
          one built over a mineral spring.
      (b) (Naut.) A depression in the bottom of a boat, into
          which water may run, and whence it is thrown out with
          a scoop.

   {Well sinker}, one who sinks or digs wells.

   {Well sinking}, the art or process of sinking or digging
      wells.

   {Well staircase} (Arch.), a staircase having a wellhole (see
      {Wellhole}
      (b) ), as distinguished from one which occupies the whole
          of the space left for it in the floor.

   {Well sweep}. Same as {Sweep}, n., 12.

   {Well water}, the water that flows into a well from
      subterraneous springs; the water drawn from a well.

Source : WordNet®

artesian well
     n : a well drilled through impermeable strata into strata that
         receive water from a higher altitude so there is pressure
         to force the water to flow upward