A hexagon has 6 sides all the same, so a cube would be a "3-D hexagon" , if you use that definition, with squares corresponding to the sides of a hexagon. There's no 3-D regular solid with all hexagonal faces. read more
A 3D hexagon is called a hexagonal prism. It has two hexagons for bases and six rectangular sides. A hexagonal prism is classified as an octahedron, which is a three-dimensional geometric object with eight faces. read more