What shape describes a casket that has eight angles or corners?

The shape that describes a casket with eight angles or corners is an octagon. An octagon is defined as a polygon with eight sides and eight angles, which is why it fits the description perfectly. This shape is often associated with certain casket designs, as its unique structure can provide a distinct aesthetic appeal.

In contrast, a rectangle has four corners, a square has four equal sides and corners, and a hexagon comprises six sides and corners. Each of these alternatives lacks the eight angles that are characteristic of an octagon, solidifying the octagon as the correct answer.