a wooded mountain in Greece, near the coast of SE Thessaly, rising to 1,548 m (5,079 ft). It was held in Greek mythology to be the home of the centaurs, and the giants were said to have piled Mounts Olympus and Ossa on its summit in their attempt to reach heaven and destroy the gods.
Phrases
pile (or heap) Pelion on Ossa
add an extra difficulty to something which is already onerous.
