icosahedron
noun
ico·sa·he·dron (ˌ)ī-ˌkō-sə-ˈhē-drən 
-ˌkä-
plural icosahedrons or icosahedra (ˌ)ī-ˌkō-sə-ˈhē-drə
-ˌkä-
: a polyhedron having 20 faces
Example Sentences
Recent Examples on the Web The symmetry group of the quasicrystal is the same as that of the regular 20-sided solid known as an icosahedron, and the chemistry is given by the formula Si61Cu30Ca7Fe2. 
David Bressan, Forbes, 18 May 2021 The arrangement of rotations which leave the objects looking unchanged is the same as that of a regular icosahedron. George Hart, Scientific American, 22 Mar. 2013 One popular design is based on the mathematical structure of an icosahedron, a three-dimensional shape built from equilateral triangles. Eugenia Cheng, WSJ, 19 Nov. 2020 Truly glorious, a 20-sided die, the icosahedron, goes back to antiquity. William Herkewitz, Popular Mechanics, 1 Sep. 2019 For that kind of math, the icosahedron was the ideal random number generator. William Herkewitz, Popular Mechanics, 1 Sep. 2019 The Florence specimen exhibited the symmetries of an icosahedron, a soccer-ball-like atomic arrangement that can be viewed from 60 different angles without any change to the structure’s overall orientation. Quanta Magazine, 13 June 2014 The immersive experience took place under a giant version of their icosahedron logo, which — Odesza explained in a Reddit thread — represents their genre and style versatility. Susie Schmank, Indianapolis Star, 30 Apr. 2018 They are defined by symmetry, and the Greeks knew that there were only five possibilities meeting the criteria: the tetrahedron, cube, octahedron, dodecahedron and icosahedron. Eugenia Cheng, WSJ, 10 Aug. 2017 See More
David Bressan, Forbes, 18 May 2021 The arrangement of rotations which leave the objects looking unchanged is the same as that of a regular icosahedron. George Hart, Scientific American, 22 Mar. 2013 One popular design is based on the mathematical structure of an icosahedron, a three-dimensional shape built from equilateral triangles. Eugenia Cheng, WSJ, 19 Nov. 2020 Truly glorious, a 20-sided die, the icosahedron, goes back to antiquity. William Herkewitz, Popular Mechanics, 1 Sep. 2019 For that kind of math, the icosahedron was the ideal random number generator. William Herkewitz, Popular Mechanics, 1 Sep. 2019 The Florence specimen exhibited the symmetries of an icosahedron, a soccer-ball-like atomic arrangement that can be viewed from 60 different angles without any change to the structure’s overall orientation. Quanta Magazine, 13 June 2014 The immersive experience took place under a giant version of their icosahedron logo, which — Odesza explained in a Reddit thread — represents their genre and style versatility. Susie Schmank, Indianapolis Star, 30 Apr. 2018 They are defined by symmetry, and the Greeks knew that there were only five possibilities meeting the criteria: the tetrahedron, cube, octahedron, dodecahedron and icosahedron. Eugenia Cheng, WSJ, 10 Aug. 2017 See More Word History
Etymology
Greek eikosaedron, from eikosi twenty + -edron -hedron — more at vigesimal
First Known Use
1570, in the meaning defined above