Definitions for "Uniaxial"
Having but one optic axis, or line of no double refraction.
Having only one axis; developing along a single line or plane; -- opposed to multiaxial.
Minerals (crystals) that have the unique property of single direction refraction or one optic axis. Because of this cutters must align rough pieces for proper visibility of the light reflection when preparing the gemstone. The stone's brilliance can be lost if axis alignment is not carefully controlled.