Prism

A prism is a shape that consists of a lower-dimensional shape extruded through a higher dimensional space. The most commonly considered prisms are the polygonal prisms, which are prisms comprising two polygons connected by rectangles.

A prism has a hyperplane of symmetry between the two end faces, as well as hyperplanes of symmetry matching the symmetry of its end face. For example, a triangular prism has four planes of symmetry: one through the middle, and three vertically through the triangle.

Antiprism[]

An antiprism is a 3-D figure which includes two parallel equal faces, and triangular faces on the sides. Based from it's context, their opposite is Prism.