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