1a mountain in Thessaly, NE Greece, south of Mount Olympus, rising to a height of 1,978 m (6,489 ft). In Greek mythology the giants were said to have piled Mount Ossa on to Mount Pelion, and vice versa, in an attempt to reach heaven and destroy the gods.
2the highest mountain on the island of Tasmania, rising to a height of 1,617 m (5,305 ft).
Ossa, Mount in other Oxford dictionaries
Definition of Ossa, Mount in the US English dictionary