1A red, crystalline hydrocarbon which is an isomer of benzene (C₆H₆) and has a molecule containing six carbon atoms arranged at the corners of a triangular prism; any of various analogues or substituted derivatives of this.

2A cluster of atoms of iron, sulphur, and/or other elements bonded together in the shape of a prism; specifically one containing six iron and six sulphur atoms. Chiefly attributive.