The Collaborative International Dictionary of English v.0.48:

Refraction \Re*frac"tion\ (r?*fr?k"sh?n), n. [F. r['e]fraction.]
   1. The act of refracting, or the state of being refracted.
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   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.
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            Refraction out of the rarer medium into the denser,
            is made towards the perpendicular.    --Sir I.
                                                  Newton.
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   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.
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   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.
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The Collaborative International Dictionary of English v.0.48:

Angle \An"gle\ ([a^][ng]"g'l), n. [F. angle, L. angulus angle,
   corner; akin to uncus hook, Gr. 'agky`los bent, crooked,
   angular, 'a`gkos a bend or hollow, AS. angel hook, fish-hook,
   G. angel, and F. anchor.]
   1. The inclosed space near the point where two lines meet; a
      corner; a nook.
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            Into the utmost angle of the world.   --Spenser.
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            To search the tenderest angles of the heart.
                                                  --Milton.
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   2. (Geom.)
      (a) The figure made by. two lines which meet.
      (b) The difference of direction of two lines. In the lines
          meet, the point of meeting is the vertex of the angle.
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   3. A projecting or sharp corner; an angular fragment.
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            Though but an angle reached him of the stone.
                                                  --Dryden.
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   4. (Astrol.) A name given to four of the twelve astrological
      "houses." [Obs.] --Chaucer.
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   5. [AS. angel.] A fishhook; tackle for catching fish,
      consisting of a line, hook, and bait, with or without a
      rod.
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            Give me mine angle: we 'll to the river there.
                                                  --Shak.
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            A fisher next his trembling angle bears. --Pope.
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   Acute angle, one less than a right angle, or less than
      90[deg].

   Adjacent or Contiguous angles, such as have one leg
      common to both angles.

   Alternate angles. See Alternate.

   Angle bar.
      (a) (Carp.) An upright bar at the angle where two faces of
          a polygonal or bay window meet. --Knight.
      (b) (Mach.) Same as Angle iron.

   Angle bead (Arch.), a bead worked on or fixed to the angle
      of any architectural work, esp. for protecting an angle of
      a wall.

   Angle brace, Angle tie (Carp.), a brace across an
      interior angle of a wooden frame, forming the hypothenuse
      and securing the two side pieces together. --Knight.

   Angle iron (Mach.), a rolled bar or plate of iron having
      one or more angles, used for forming the corners, or
      connecting or sustaining the sides of an iron structure to
      which it is riveted.

   Angle leaf (Arch.), a detail in the form of a leaf, more or
      less conventionalized, used to decorate and sometimes to
      strengthen an angle.

   Angle meter, an instrument for measuring angles, esp. for
      ascertaining the dip of strata.

   Angle shaft (Arch.), an enriched angle bead, often having a
      capital or base, or both.

   Curvilineal angle, one formed by two curved lines.

   External angles, angles formed by the sides of any
      right-lined figure, when the sides are produced or
      lengthened.

   Facial angle. See under Facial.

   Internal angles, those which are within any right-lined
      figure.

   Mixtilineal angle, one formed by a right line with a curved
      line.

   Oblique angle, one acute or obtuse, in opposition to a
      right angle.

   Obtuse angle, one greater than a right angle, or more than
      90[deg].

   Optic angle. See under Optic.

   Rectilineal or Right-lined angle, one formed by two right
      lines.

   Right angle, one formed by a right line falling on another
      perpendicularly, or an angle of 90[deg] (measured by a
      quarter circle).

   Solid angle, the figure formed by the meeting of three or
      more plane angles at one point.

   Spherical angle, one made by the meeting of two arcs of
      great circles, which mutually cut one another on the
      surface of a globe or sphere.

   Visual angle, the angle formed by two rays of light, or two
      straight lines drawn from the extreme points of an object
      to the center of the eye.

   For Angles of commutation, draught, incidence,
   reflection, refraction, position, repose, fraction,
      see Commutation, Draught, Incidence, Reflection,
      Refraction, etc.
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WordNet (r) 3.0 (2006):

refraction
    n 1: the change in direction of a propagating wave (light or
         sound) when passing from one medium to another
    2: the amount by which a propagating wave is bent [syn:
       deflection, deflexion, refraction]

Moby Thesaurus II by Grady Ward, 1.0:

18 Moby Thesaurus words for "refraction":
   atmospheric attenuation, blind spots, clutter, deflection,
   deflexure, diffraction, diffusion, dispersion, distortion,
   false echoes, flection, flexure, ground clutter, scatter,
   sea clutter, skewness, superrefraction, torsion