The Collaborative International Dictionary of English v.0.48:

Gauge \Gauge\, n. [Written also gage.]
   1. A measure; a standard of measure; an instrument to
      determine dimensions, distance, or capacity; a standard.
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            This plate must be a gauge to file your worm and
            groove to equal breadth by.           --Moxon.
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            There is not in our hands any fixed gauge of minds.
                                                  --I. Taylor.
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   2. Measure; dimensions; estimate.
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            The gauge and dimensions of misery, depression, and
            contempt.                             --Burke.
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   3. (Mach. & Manuf.) Any instrument for ascertaining or
      regulating the dimensions or forms of things; a templet or
      template; as, a button maker's gauge.
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   4. (Physics) Any instrument or apparatus for measuring the
      state of a phenomenon, or for ascertaining its numerical
      elements at any moment; -- usually applied to some
      particular instrument; as, a rain gauge; a steam gauge.
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   5. (Naut.)
      (a) Relative positions of two or more vessels with
          reference to the wind; as, a vessel has the weather
          gauge of another when on the windward side of it, and
          the lee gauge when on the lee side of it.
      (b) The depth to which a vessel sinks in the water.
          --Totten.
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   6. The distance between the rails of a railway.
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   Note: The standard gauge of railroads in most countries is
         four feet, eight and one half inches. Wide, or broad,
         gauge, in the United States, is six feet; in England,
         seven feet, and generally any gauge exceeding standard
         gauge. Any gauge less than standard gauge is now called
         narrow gauge. It varies from two feet to three feet six
         inches.
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   7. (Plastering) The quantity of plaster of Paris used with
      common plaster to accelerate its setting.
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   8. (Building) That part of a shingle, slate, or tile, which
      is exposed to the weather, when laid; also, one course of
      such shingles, slates, or tiles.
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   Gauge of a carriage, car, etc., the distance between the
      wheels; -- ordinarily called the track.

   Gauge cock, a stop cock used as a try cock for ascertaining
      the height of the water level in a steam boiler.

   Gauge concussion (Railroads), the jar caused by a car-wheel
      flange striking the edge of the rail.

   Gauge glass, a glass tube for a water gauge.

   Gauge lathe, an automatic lathe for turning a round object
      having an irregular profile, as a baluster or chair round,
      to a templet or gauge.

   Gauge point, the diameter of a cylinder whose altitude is
      one inch, and contents equal to that of a unit of a given
      measure; -- a term used in gauging casks, etc.

   Gauge rod, a graduated rod, for measuring the capacity of
      barrels, casks, etc.

   Gauge saw, a handsaw, with a gauge to regulate the depth of
      cut. --Knight.

   Gauge stuff, a stiff and compact plaster, used in making
      cornices, moldings, etc., by means of a templet.

   Gauge wheel, a wheel at the forward end of a plow beam, to
      determine the depth of the furrow.

   Joiner's gauge, an instrument used to strike a line
      parallel to the straight side of a board, etc.

   Printer's gauge, an instrument to regulate the length of
      the page.

   Rain gauge, an instrument for measuring the quantity of
      rain at any given place.

   Salt gauge, or Brine gauge, an instrument or contrivance
      for indicating the degree of saltness of water from its
      specific gravity, as in the boilers of ocean steamers.

   Sea gauge, an instrument for finding the depth of the sea.


   Siphon gauge, a glass siphon tube, partly filled with
      mercury, -- used to indicate pressure, as of steam, or the
      degree of rarefaction produced in the receiver of an air
      pump or other vacuum; a manometer.

   Sliding gauge. (Mach.)
      (a) A templet or pattern for gauging the commonly accepted
          dimensions or shape of certain parts in general use,
          as screws, railway-car axles, etc.
      (b) A gauge used only for testing other similar gauges,
          and preserved as a reference, to detect wear of the
          working gauges.
      (c) (Railroads) See Note under Gauge, n., 5.

   Star gauge (Ordnance), an instrument for measuring the
      diameter of the bore of a cannon at any point of its
      length.

   Steam gauge, an instrument for measuring the pressure of
      steam, as in a boiler.

   Tide gauge, an instrument for determining the height of the
      tides.

   Vacuum gauge, a species of barometer for determining the
      relative elasticities of the vapor in the condenser of a
      steam engine and the air.

   Water gauge.
      (a) A contrivance for indicating the height of a water
          surface, as in a steam boiler; as by a gauge cock or
          glass.
      (b) The height of the water in the boiler.

   Wind gauge, an instrument for measuring the force of the
      wind on any given surface; an anemometer.

   Wire gauge, a gauge for determining the diameter of wire or
      the thickness of sheet metal; also, a standard of size.
      See under Wire.
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The Collaborative International Dictionary of English v.0.48:

Gauge \Gauge\ (g[=a]j), v. t. [imp. & p. p. Gauged; p. pr. &
   vb. n. Gauging] [OF. gaugier, F. jauger, cf. OF. gauge
   gauge, measuring rod, F. jauge; of uncertain origin; perh.
   fr. an assumed L. qualificare to determine the qualities of a
   thing (see Qualify); but cf. also F. jalon a measuring
   stake in surveying, and E. gallon.] [Written also gage.]
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   1. To measure or determine with a gauge.
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   2. To measure or to ascertain the contents or the capacity
      of, as of a pipe, barrel, or keg.
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   3. (Mech.) To measure the dimensions of, or to test the
      accuracy of the form of, as of a part of a gunlock.
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            The vanes nicely gauged on each side. --Derham.
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   4. To draw into equidistant gathers by running a thread
      through it, as cloth or a garment.
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   5. To measure the capacity, character, or ability of; to
      estimate; to judge of.
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            You shall not gauge me
            By what we do to-night.               --Shak.
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WordNet (r) 3.0 (2006):

gauge
    n 1: a measuring instrument for measuring and indicating a
         quantity such as the thickness of wire or the amount of
         rain etc. [syn: gauge, gage]
    2: accepted or approved instance or example of a quantity or
       quality against which others are judged or measured or
       compared [syn: gauge, standard of measurement]
    3: the distance between the rails of a railway or between the
       wheels of a train
    4: the thickness of wire
    5: diameter of a tube or gun barrel [syn: bore, gauge,
       caliber, calibre]
    v 1: judge tentatively or form an estimate of (quantities or
         time); "I estimate this chicken to weigh three pounds"
         [syn: estimate, gauge, approximate, guess, judge]
    2: rub to a uniform size; "gauge bricks"
    3: determine the capacity, volume, or contents of by measurement
       and calculation; "gauge the wine barrels"
    4: measure precisely and against a standard; "the wire is
       gauged"
    5: adapt to a specified measurement; "gauge the instruments"
    6: mix in specific proportions; "gauge plaster"

Moby Thesaurus II by Grady Ward, 1.0:

168 Moby Thesaurus words for "gauge":
   Johansson block, T square, adjust, amount, amplitude, appraise,
   appreciate, area, assay, assess, barometer, basis, benchmark,
   bigness, body, breadth, bulk, calculate, caliber, calibrate,
   caliper, calipers, call, canon, capacity, catalog, categorize,
   chain, check, check a parameter, class, classify, compass, compute,
   coverage, criterion, degree, depth, determine, dial, diameter,
   dimension, dimensions, dipstick, divide, dividers, enlarge,
   estimate, evaluate, example, expanse, expansion, extension, extent,
   factor, fathom, feeler gauge, figure, foot rule, form an estimate,
   gage, gauge block, gauger, girth, give an appreciation, goniometer,
   grade, gradiometer, graduate, graduated scale, greatness, group,
   guess, guide, guideline, height, identify, instrument, judge,
   largeness, length, level, limit, line, litmus test, log, log line,
   magnitude, make an estimation, mark, mass, match, measure,
   measurement, measurer, mensurate, mete, meter, meterstick,
   micrometer, model, norm, octant, pace, parameter, pattern, plumb,
   plumb rule, prize, probe, proportion, proportions, protractor,
   quadrant, quantify, quantity, quantize, radius, range, rank, rate,
   reach, reading, readout, reckon, rod, rule, ruler, scale, scope,
   sector, set square, sextant, sift, size, size up, sort, sort out,
   sound, span, spirit level, spread, square, standard, step, survey,
   take a reading, tape, tape measure, tapeline, test, theodolite,
   thrash out, touchstone, transit, transit theodolite, triangulate,
   try square, type, valuate, value, vernier, vernier caliper, volume,
   weigh, width, winnow, yardstick