Lewis Short
circĭnātĭo (noun F) : circino (lit. the describing of a circle; hence, concrete)
* The circumference of a circle, a circle (a word of Vitr.): linea circinationis,Vitr. 1, 6, 6: circuli,id. 9, 7, 2; 3, 3; 10, 10 al.—Of the circular path of the planets, Vitr. 9, 4, pp. 264, 266 Bip.
Charlton T. Lewis, Charles Short, A Latin Dictionary