[1] : The Collaborative International Dictionary of English v.0.48

refraction \refrac"tion\ r?fr?k"sh?n, n. f. r'efraction.
   1. the act of refracting, or the state of being refracted.
      1913 webster

   2. the change in the direction of ray of light, heat, or the
      like, when it enters obliquely a medium of a different
      density from that through which it has previously moved.
      1913 webster

            refraction out of the rarer medium into the denser,
            is made towards the perpendicular.    --sir i.
                                                  newton.
      1913 webster

   3. astron.
      a the change in the direction of a ray of light, and,
          consequently, in the apparent position of a heavenly
          body from which it emanates, arising from its passage
          through the earth's atmosphere; -- hence distinguished
          as atmospheric refraction, or astronomical refraction.
      b the correction which is to be deducted from the
          apparent altitude of a heavenly body on account of
          atmospheric refraction, in order to obtain the true
          altitude.
          1913 webster

   angle of refraction opt., the angle which a refracted ray
      makes with the perpendicular to the surface separating the
      two media traversed by the ray.

   conical refraction opt., the refraction of a ray of light
      into an infinite number of rays, forming a hollow cone.
      this occurs when a ray of light is passed through crystals
      of some substances, under certain circumstances. conical
      refraction is of two kinds; external conical refraction,
      in which the ray issues from the crystal in the form of a
      cone, the vertex of which is at the point of emergence;
      and internal conical refraction, in which the ray is
      changed into the form of a cone on entering the crystal,
      from which it issues in the form of a hollow cylinder.
      this singular phenomenon was first discovered by sir w. r.
      hamilton by mathematical reasoning alone, unaided by
      experiment.

   differential refraction astron., the change of the
      apparent place of one object relative to a second object
      near it, due to refraction; also, the correction required
      to be made to the observed relative places of the two
      bodies.

   double refraction opt., the refraction of light in two
      directions, which produces two distinct images. the power
      of double refraction is possessed by all crystals except
      those of the isometric system. a uniaxial crystal is said
      to be optically positive like quartz, or optically
      negative like calcite, or to have positive, or negative,
      double refraction, according as the optic axis is the axis
      of least or greatest elasticity for light; a biaxial
      crystal is similarly designated when the same relation
      holds for the acute bisectrix.

   index of refraction. see under index.

   refraction circle opt., an instrument provided with a
      graduated circle for the measurement of refraction.

   refraction of latitude, longitude, declination, right
   ascension, etc., the change in the apparent latitude,
      longitude, etc., of a heavenly body, due to the effect of
      atmospheric refraction.

   terrestrial refraction, the change in the apparent altitude
      of a distant point on or near the earth's surface, as the
      top of a mountain, arising from the passage of light from
      it to the eye through atmospheric strata of varying
      density.
      1913 webster
see also:
angle of refraction conical refraction differential refraction double refraction index of refraction index 
refraction circle refraction of latitude longitude declination right ascension 
terrestrial refraction 

[2] : WordNet (r) 2.0

angle of refraction
     n : the angle between a refracted ray and a line perpendicular
         to the surface between the two media at the point of
         refraction

Angle >> A Words
Angle, definition of term: Angle
angle_pag1.html

Angle Bracket >> A Words
Angle Bracket, definition of term: Angle Bracket
angle+bracket_pag1.html

Angle Iron >> A Words
Angle Iron, definition of term: Angle Iron
angle+iron_pag1.html

Acute Angle >> A Words
Acute Angle, definition of term: Acute Angle
acute+angle_pag1.html

Dihedral Angle >> D Words
Dihedral Angle, definition of term: Dihedral Angle
dihedral+angle_pag1.html

Angle Of Attack >> A Words
Angle Of Attack, definition of term: Angle Of Attack
angle+of+attack_pag1.html

Angle Of Repose >> A Words
Angle Of Repose, definition of term: Angle Of Repose
angle+of+repose_pag1.html