icosahedron

noun

Etymology: From Ancient Greek εἰκοσάεδρον (eikosáedron), from εἴκοσι (eíkosi, “twenty”) + ἕδρα (hédra, “face of a geometrical solid”). Equivalent to icosa- + -hedron.

1. A polyhedron with twenty faces.
2. A regular icosahedron: one of the Platonic solids, all of whose faces are regular (equilateral) triangles