Uniaxial \U`ni*ax"i*al\, a. [Uni + axial.]
   1. (Crystallog.) Having but one optic axis, or line of no
      double refraction.
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   Note: In uniaxial crystals, the optic axis has the direction
         of the vertical crystallographic axis. All tetragonal
         and hexagonal crystals are uniaxial.
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   2. (Biol.) Having only one axis; developing along a single
      line or plane; -- opposed to multiaxial.
      [1913 Webster]