Amp-sanctus (better than Am-), i, m.,
a lake in Italy , highly dangerous from its pestiferous exhalations (hence, in the poets, the entrance to the infernal regions), now Le Mofete or Lago d’Ansante , Verg. A. 7, 565; Cic. Div. 1, 36; Plin. 2, 93, 95, § 208.
Ampsānctus (Am-) ī, m see ambi-, all hallowed (sc. lacus), a lake of Italy, noted for pestiferous...
An Elementary Latin Dictionary