n. [ Gr. &unr_;; &unr_; twenty + &unr_; seat, base, fr. &unr_; to sit. ] (Geom.) A solid bounded by twenty sides or faces. [ 1913 Webster ]
Regular icosahedron, one of the five regular polyhedrons, bounded by twenty equilateral triangules. Five triangles meet to form each solid angle of the polyhedron. [ 1913 Webster ]