in Greek mythology, is
(1) the name of the sea, which is the source of the Acheron river in Epirus.
(2.) A sea near Cumae, in Italy.
(3.) A cave in the vicinity of the city of Heraclea in Bithynia, by which Hercules is said to have entered the lower regions.
(4.) A sea near Memphis across which the Egyptians ferried their dead, either to bury them on the other shore or to cast them into the water.