the GNU version of the Collaborative International Dictionary of English
adj. In the form of a hexahedron; having six sides or faces.
The Century Dictionary and Cyclopedia
Having the figure of a hexahedron; having six equal superficial sides or faces; cubic.
In entomology, having six distinct and more or less parallel sides; six-sided: said of long bodies, as joints of the antennæ, etc.
Word Usage
"One of the masses of ice which he describes was crystallised in prisms of various numbers of sides: of these prisms the greater part were hexahedral and irregular."