The Collaborative International Dictionary of English v.0.48:

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.]
   [1913 Webster]
   1. An issue of water from the earth; a spring; a fountain.
      [1913 Webster]

            Begin, then, sisters of the sacred well. --Milton.
      [1913 Webster]

   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.
      [1913 Webster]

            The woman said unto him, Sir, thou hast nothing to
            draw with, and the well is deep.      --John iv. 11.
      [1913 Webster]

   3. A shaft made in the earth to obtain oil or brine.
      [1913 Webster]

   4. Fig.: A source of supply; fountain; wellspring. "This well
      of mercy." --Chaucer.
      [1913 Webster]

            Dan Chaucer, well of English undefiled. --Spenser.
      [1913 Webster]

            A well of serious thought and pure.   --Keble.
      [1913 Webster]

   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.
          [1913 Webster]

   6. (Mil.) A hole or excavation in the earth, in mining, from
      which run branches or galleries.
      [1913 Webster]

   7. (Arch.) An opening through the floors of a building, as
      for a staircase or an elevator; a wellhole.
      [1913 Webster]

   8. (Metal.) The lower part of a furnace, into which the metal
      falls.
      [1913 Webster]

   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.
      [1913 Webster]

WordNet (r) 3.0 (2006):

well water
    n 1: underground water that is held in the soil and in pervious
         rocks [syn: ground water, spring water, well water]