The Collaborative International Dictionary of English v.0.48:

Surface \Sur"face`\, n. [F. See Sur-, and Face, and cf.
   Superficial.]
   1. The exterior part of anything that has length and breadth;
      one of the limits that bound a solid, esp. the upper face;
      superficies; the outside; as, the surface of the earth;
      the surface of a diamond; the surface of the body.
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            The bright surface of this ethereous mold. --Milton.
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   2. Hence, outward or external appearance.
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            Vain and weak understandings, which penetrate no
            deeper than the surface.              --V. Knox.
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   3. (Geom.) A magnitude that has length and breadth without
      thickness; superficies; as, a plane surface; a spherical
      surface.
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   4. (Fort.) That part of the side which is terminated by the
      flank prolonged, and the angle of the nearest bastion.
      --Stocqueler.
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   Caustic surface, Heating surface, etc. See under
      Caustic, Heating, etc.

   Surface condensation, Surface condenser. See under
      Condensation, and Condenser.

   Surface gauge (Mach.), an instrument consisting of a
      standard having a flat base and carrying an adjustable
      pointer, for gauging the evenness of a surface or its
      height, or for marking a line parallel with a surface.

   Surface grub (Zool.), the larva of the great yellow
      underwing moth (Triphoena pronuba). It is often
      destructive to the roots of grasses and other plants.

   Surface plate (Mach.), a plate having an accurately dressed
      flat surface, used as a standard of flatness by which to
      test other surfaces.

   Surface printing, printing from a surface in relief, as
      from type, in distinction from plate printing, in which
      the ink is contained in engraved lines.
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The Collaborative International Dictionary of English v.0.48:

Caustic \Caus"tic\, Caustical \Caus"tic*al\, a. [L. caustucs,
   Ge. ?, fr. ? to burn. Cf. Calm, Ink.]
   1. Capable of destroying the texture of anything or eating
      away its substance by chemical action; burning; corrosive;
      searing.
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   2. Severe; satirical; sharp; as, a caustic remark.
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   Caustic curve (Optics), a curve to which the ray of light,
      reflected or refracted by another curve, are tangents, the
      reflecting or refracting curve and the luminous point
      being in one plane.

   Caustic lime. See under Lime.

   Caustic potash, Caustic soda (Chem.), the solid
      hydroxides potash, KOH, and soda, NaOH, or solutions
      of the same.

   Caustic silver, nitrate of silver, lunar caustic.

   Caustic surface (Optics), a surface to which rays reflected
      or refracted by another surface are tangents. Caustic
      curves and surfaces are called catacaustic when formed by
      reflection, and diacaustic when formed by refraction.

   Syn: Stinging; cutting; pungent; searching.
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