Source : Webster's Revised Unabridged Dictionary (1913)

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.

            The bright surface of this ethereous mold. --Milton.

   2. Hence, outward or external appearance.

            Vain and weak understandings, which penetrate no
            deeper than the surface.              --V. Knox.

   3. (Geom.) A magnitude that has length and breadth without
      thickness; superficies; as, a plane surface; a spherical
      surface.

   4. (Fort.) That part of the side which is terminated by the
      flank prolonged, and the angle of the nearest bastion.
      --Stocqueler.

   {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} (Zo["o]l.), the larva of the great yellow
      underwing moth ({Triph[oe]na 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.

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.

   2. Severe; satirical; sharp; as, a caustic remark.

   {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.