The motion of a point, line, or surface about a point
   or line as its center or axis, in such a manner that a moving point
   generates a curve, a moving line a surface (called a surface of
   revolution), and a moving surface a solid (called a solid of
   revolution); as, the revolution of a right-angled triangle about one of
   its sides generates a cone; the revolution of a semicircle about the
   diameter generates a sphere.