The Collaborative International Dictionary of English v.0.48:

Shear \Shear\, n. [AS. sceara. See Shear, v. t.]
   1. A pair of shears; -- now always used in the plural, but
      formerly also in the singular. See Shears.
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            On his head came razor none, nor shear. --Chaucer.
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            Short of the wool, and naked from the shear.
                                                  --Dryden.
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   2. A shearing; -- used in designating the age of sheep.
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            After the second shearing, he is a two-shear ram; .
            . . at the expiration of another year, he is a
            three-shear ram; the name always taking its date
            from the time of shearing.            --Youatt.
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   3. (Engin.) An action, resulting from applied forces, which
      tends to cause two contiguous parts of a body to slide
      relatively to each other in a direction parallel to their
      plane of contact; -- also called shearing stress, and
      tangential stress.
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   4. (Mech.) A strain, or change of shape, of an elastic body,
      consisting of an extension in one direction, an equal
      compression in a perpendicular direction, with an
      unchanged magnitude in the third direction.
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   Shear blade, one of the blades of shears or a shearing
      machine.

   Shear hulk. See under Hulk.

   Shear steel, a steel suitable for shears, scythes, and
      other cutting instruments, prepared from fagots of
      blistered steel by repeated heating, rolling, and tilting,
      to increase its malleability and fineness of texture.
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The Collaborative International Dictionary of English v.0.48:

Tangential \Tan*gen"tial\, a. (Geom.)
   Of or pertaining to a tangent; in the direction of a tangent.
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   Tangential force (Mech.), a force which acts on a moving
      body in the direction of a tangent to the path of the
      body, its effect being to increase or diminish the
      velocity; -- distinguished from a normal force, which acts
      at right angles to the tangent and changes the direction
      of the motion without changing the velocity.

   Tangential stress. (Engin.) See Shear, n., 3.
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