Lewis & Short

Mūgĭōnĭa or Mūgōnĭa, ae, or Mūgĭōnis (Mucionis), is, f. (porta), a gate of ancient Rome, which was afterwards within the city: in Palatio Mucionis a mugitu, Varr. L. L. 5, § 164 Müll.: Mugionia porta Romae dicta est a Mugio quodam. Paul. ex Fest. p. 144 Müll.; Sol. 1, 24; cf. Becker’s Antiq. 1, p. 109 sq.