uniaxial Syllabification: (u·ni·ax·i·al)Pronunciation: /ˌyo͞onēˈaksēəl/Definition of uniaxial adjective having or relating to a single axis. (of crystals) having one optic axis, as in the hexagonal, trigonal, and tetragonal systems. uniaxial in other Oxford dictionaries Definition of uniaxial in the British & World English dictionary