icosahedron

• eicosaedrum (obsolete)
• icosaedrum (obsolete)

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

• IPA^(key): /ˌaɪkoʊsəˈhiːdɹən/, /ˌaɪkɒsəˈhiːdɹən/, /ˌaɪkɔsəˈhiːdɹən/

icosahedron (plural icosahedra or icosahedrons)

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

   Synonym: regular gyroelongated pentagonal bipyramid

• icosahedral
• icosahedrite