The Collaborative International Dictionary of English v.0.48:

field \field\ (f[=e]ld), n. [OE. feld, fild, AS. feld; akin to
   D. veld, G. feld, Sw. f[aum]lt, Dan. felt, Icel. fold field
   of grass, AS. folde earth, land, ground, OS. folda.]
   1. Cleared land; land suitable for tillage or pasture;
      cultivated ground; the open country.
      [1913 Webster]

   2. A piece of land of considerable size; esp., a piece
      inclosed for tillage or pasture.
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            Fields which promise corn and wine.   --Byron.
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   3. A place where a battle is fought; also, the battle itself.
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            In this glorious and well-foughten field. --Shak.
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            What though the field be lost?        --Milton.
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   4. An open space; an extent; an expanse. Esp.:
      (a) Any blank space or ground on which figures are drawn
          or projected.
      (b) The space covered by an optical instrument at one
          view; as, wide-field binoculars.
          [1913 Webster + PJC]

                Without covering, save yon field of stars.
                                                  --Shak.
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                Ask of yonder argent fields above. --Pope.
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   5. (Her.) The whole surface of an escutcheon; also, so much
      of it is shown unconcealed by the different bearings upon
      it. See Illust. of Fess, where the field is represented
      as gules (red), while the fess is argent (silver).
      [1913 Webster]

   6. An unresticted or favorable opportunity for action,
      operation, or achievement; province; room.
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            Afforded a clear field for moral experiments.
                                                  --Macaulay.
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   7. (Sports) An open, usually flat, piece of land on which a
      sports contest is played; a playing field; as, a football
      field; a baseball field.

   Syn: playing field, athletic field, playing area.
        [PJC]

   8. Specifically: (Baseball) That part of the grounds reserved
      for the players which is outside of the diamond; -- called
      also outfield.
      [1913 Webster]

   9. A geographic region (land or sea) which has some notable
      feature, activity or valuable resource; as, the diamond
      fields of South Africa; an oil field; a gold field; an ice
      field.
      [WordNet 1.6]

   10. A facility having an airstrip where airplanes can take
       off and land; an airfield.

   Syn: airfield, landing field, flying field, aerodrome.
        [WordNet 1.6]

   11. A collective term for all the competitors in any outdoor
       contest or trial, or for all except the favorites in the
       betting.
       [1913 Webster]

   12. A branch of knowledge or sphere of activity; especially,
       a learned or professional discipline; as, she's an expert
       in the field of geology; in what field did she get her
       doctorate?; they are the top company in the field of
       entertainment.

   Syn: discipline, subject, subject area, subject field, field
        of study, study, branch of knowledge.
        [WordNet 1.6]

   Note: Within the master text files of this electronic
         dictionary, where a word is used in a specific sense in
         some specialized field of knowledge, that field is
         indicated by the tags: () preceding that sense of the
         word.
         [PJC]

   13. A location, usually outdoors, away from a studio or
       office or library or laboratory, where practical work is
       done or data is collected; as, anthropologists do much of
       their work in the field; the paleontologist is in the
       field collecting specimens. Usually used in the phrase

   in the field.
      [WordNet 1.6]

   14. (Physics) The influence of a physical object, such as an
       electrically charged body, which is capable of exerting
       force on objects at a distance; also, the region of space
       over which such an influence is effective; as, the
       earth's gravitational field; an electrical field; a
       magnetic field; a force field.
       [PJC]

   15. (Math.) A set of elements within which operations can be
       defined analagous to the operations of addition,
       subtraction, multiplication, and division on the real
       numbers; within such a set of elements addition and
       multiplication are commutative and associative and
       multiplication is distributive over addition and there
       are two elements 0 and 1; a commutative division ring;
       as, the set of all rational numbers is a field.
       [WordNet 1.6]

   Note: Field is often used adjectively in the sense of
         belonging to, or used in, the fields; especially with
         reference to the operations and equipments of an army
         during a campaign away from permanent camps and
         fortifications. In most cases such use of the word is
         sufficiently clear; as, field battery; field
         fortification; field gun; field hospital, etc. A field
         geologist, naturalist, etc., is one who makes
         investigations or collections out of doors. A survey
         uses a field book for recording field notes, i.e.,
         measurment, observations, etc., made in field work
         (outdoor operations). A farmer or planter employs field
         hands, and may use a field roller or a field derrick.
         Field sports are hunting, fishing, athletic games, etc.
         [1913 Webster]

   Coal field (Geol.) See under Coal.

   Field artillery, light ordnance mounted on wheels, for the
      use of a marching army.

   Field basil (Bot.), a plant of the Mint family (Calamintha
      Acinos); -- called also basil thyme.

   Field colors (Mil.), small flags for marking out the
      positions for squadrons and battalions; camp colors.

   Field cricket (Zool.), a large European cricket (Gryllus
      campestric), remarkable for its loud notes.

   Field day.
       (a) A day in the fields.
       (b) (Mil.) A day when troops are taken into the field for
           instruction in evolutions. --Farrow.
       (c) A day of unusual exertion or display; a gala day.

   Field driver, in New England, an officer charged with the
      driving of stray cattle to the pound.

   Field duck (Zool.), the little bustard (Otis tetrax),
      found in Southern Europe.

   Field glass. (Optics)
       (a) A binocular telescope of compact form; a lorgnette; a
           race glass.
       (b) A small achromatic telescope, from 20 to 24 inches
           long, and having 3 to 6 draws.
       (c) See Field lens.

   Field lark. (Zool.)
       (a) The skylark.
       (b) The tree pipit.

   Field lens (Optics), that one of the two lenses forming the
      eyepiece of an astronomical telescope or compound
      microscope which is nearer the object glass; -- called
      also field glass.

   Field madder (Bot.), a plant (Sherardia arvensis) used in
      dyeing.

   Field marshal (Mil.), the highest military rank conferred
      in the British and other European armies.

   Field officer (Mil.), an officer above the rank of captain
      and below that of general.

   Field officer's court (U.S.Army), a court-martial
      consisting of one field officer empowered to try all
      cases, in time of war, subject to jurisdiction of garrison
      and regimental courts. --Farrow.

   Field plover (Zool.), the black-bellied plover (Charadrius
      squatarola); also sometimes applied to the Bartramian
      sandpiper (Bartramia longicauda).

   Field spaniel (Zool.), a small spaniel used in hunting
      small game.

   Field sparrow. (Zool.)
       (a) A small American sparrow (Spizella pusilla).
       (b) The hedge sparrow. [Eng.]

   Field staff (Mil.), a staff formerly used by gunners to
      hold a lighted match for discharging a gun.

   Field vole (Zool.), the European meadow mouse.

   Field of ice, a large body of floating ice; a pack.

   Field, or Field of view, in a telescope or microscope,
      the entire space within which objects are seen.

   Field magnet. see under Magnet.

   Magnetic field. See Magnetic.

   To back the field, or To bet on the field. See under
      Back, v. t. -- To keep the field.
       (a) (Mil.) To continue a campaign.
       (b) To maintain one's ground against all comers.

   To lay against the field or To back against the field, to
      bet on (a horse, etc.) against all comers.

   To take the field (Mil.), to enter upon a campaign.
      [1913 Webster]

WordNet (r) 3.0 (2006):

field glass
    n 1: a small refracting telescope [syn: field glass, glass,
         spyglass]