二十面體
Icosahedron \I`co*sa*he"dron\, n. [Gr. ?; ? twenty + ? seat, base, fr. ? to sit.] (Geom.) A solid bounded by twenty sides or faces. {Regular icosahedron}, one of the five regular polyhedrons, bounded by twenty equilateral triangules. Five triangles meet to form each solid angle of the polyhedron.
icosahedron n : any polyhedron having twenty plane faces [also: {icosahedra} (pl)]