Word Study
biaxial
CIDE DICTIONARY
biaxial, a. [Pref. bi- + axal, axial.].
Having two axes; as, biaxial polarization; biaxial crystals. [1913 Webster]
OXFORD DICTIONARY
biaxial, adj. (esp. of crystals) having two axes along which polarized light travels with equal velocity.
For further exploring for "biaxial" in Webster Dictionary Online