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.

Source: Webster's Revised Unabridged Dictionary (1913)