a. [f. BI- pref.2 1 + AXIAL.] Having two (optic) axes.

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1854.  J. Hogg, Microsc., I. ii. (1867), 146. Topaz, a biaxial crystal.

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c. 1865.  J. Wylde, in Circ. Sc., I. 84/1. Nitre … is … a biaxial crystal.

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