The Collaborative International Dictionary of English v.0.48:

Zero \Ze"ro\, n.; pl. Zerosor Zeroes. [F. z['e]ro, from Ar.
   [,c]afrun, [,c]ifrun, empty, a cipher. Cf. Cipher.]
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   1. (Arith.) A cipher; nothing; naught.
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   2. The point from which the graduation of a scale, as of a
      thermometer, commences.
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   Note: Zero in the Centigrade, or Celsius thermometer, and in
         the R['e]aumur thermometer, is at the point at which
         water congeals. The zero of the Fahrenheit thermometer
         is fixed at the point at which the mercury stands when
         immersed in a mixture of snow and common salt. In
         Wedgwood's pyrometer, the zero corresponds with
         1077[deg] on the Fahrenheit scale. See Illust. of
         Thermometer.
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   3. Fig.: The lowest point; the point of exhaustion; as, his
      patience had nearly reached zero.
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   Absolute zero. See under Absolute.

   Zero method (Physics), a method of comparing, or measuring,
      forces, electric currents, etc., by so opposing them that
      the pointer of an indicating apparatus, or the needle of a
      galvanometer, remains at, or is brought to, zero, as
      contrasted with methods in which the deflection is
      observed directly; -- called also null method.

   Zero point, the point indicating zero, or the commencement
      of a scale or reckoning.
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The Collaborative International Dictionary of English v.0.48:

Absolute \Ab"so*lute\, a. [L. absolutus, p. p. of absolvere: cf.
   F. absolu. See Absolve.]
   1. Loosed from any limitation or condition; uncontrolled;
      unrestricted; unconditional; as, absolute authority,
      monarchy, sovereignty, an absolute promise or command;
      absolute power; an absolute monarch.
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   2. Complete in itself; perfect; consummate; faultless; as,
      absolute perfection; absolute beauty.
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            So absolute she seems,
            And in herself complete.              --Milton.
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   3. Viewed apart from modifying influences or without
      comparison with other objects; actual; real; -- opposed to
      relative and comparative; as, absolute motion;
      absolute time or space.
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   Note: Absolute rights and duties are such as pertain to man
         in a state of nature as contradistinguished from
         relative rights and duties, or such as pertain to him
         in his social relations.
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   4. Loosed from, or unconnected by, dependence on any other
      being; self-existent; self-sufficing.
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   Note: In this sense God is called the Absolute by the Theist.
         The term is also applied by the Pantheist to the
         universe, or the total of all existence, as only
         capable of relations in its parts to each other and to
         the whole, and as dependent for its existence and its
         phenomena on its mutually depending forces and their
         laws.
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   5. Capable of being thought or conceived by itself alone;
      unconditioned; non-relative.
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   Note: It is in dispute among philosopher whether the term, in
         this sense, is not applied to a mere logical fiction or
         abstraction, or whether the absolute, as thus defined,
         can be known, as a reality, by the human intellect.
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               To Cusa we can indeed articulately trace, word
               and thing, the recent philosophy of the absolute.
                                                  --Sir W.
                                                  Hamilton.
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   6. Positive; clear; certain; not doubtful. [R.]
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            I am absolute 't was very Cloten.     --Shak.
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   7. Authoritative; peremptory. [R.]
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            The peddler stopped, and tapped her on the head,
            With absolute forefinger, brown and ringed. --Mrs.
                                                  Browning.
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   8. (Chem.) Pure; unmixed; as, absolute alcohol.
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   9. (Gram.) Not immediately dependent on the other parts of
      the sentence in government; as, the case absolute. See
      Ablative absolute, under Ablative.
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   Absolute curvature (Geom.), that curvature of a curve of
      double curvature, which is measured in the osculating
      plane of the curve.

   Absolute equation (Astron.), the sum of the optic and
      eccentric equations.

   Absolute space (Physics), space considered without relation
      to material limits or objects.

   Absolute terms. (Alg.), such as are known, or which do not
      contain the unknown quantity. --Davies & Peck.

   Absolute temperature (Physics), the temperature as measured
      on a scale determined by certain general thermo-dynamic
      principles, and reckoned from the absolute zero.

   Absolute zero (Physics), the be ginning, or zero point, in
      the scale of absolute temperature. It is equivalent to
      -273[deg] centigrade or -459.4[deg] Fahrenheit.
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   Syn: Positive; peremptory; certain; unconditional; unlimited;
        unrestricted; unqualified; arbitrary; despotic;
        autocratic.
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WordNet (r) 3.0 (2006):

absolute zero
    n 1: (cryogenics) the lowest temperature theoretically
         attainable (at which the kinetic energy of atoms and
         molecules is minimal); 0 Kelvin or -273.15 centigrade or
         -459.67 Fahrenheit

Moby Thesaurus II by Grady Ward, 1.0:

38 Moby Thesaurus words for "absolute zero":
   algidity, bitterness, bleakness, boiling point, briskness, chill,
   chilliness, cold, coldness, cool, coolness, coolth, crispness,
   cryogenics, cryology, decrease in temperature, dew point,
   freezing point, freshness, frigidity, frostiness, gelidity,
   iciness, inclemency, intense cold, keenness, low temperature,
   melting point, nip, nippiness, rawness, recalescence point, rigor,
   severity, sharp air, sharpness, temperature, zero