Meaning of NATURAL DEPRESSION

WordNet Dictionary
	Definition:		[n]  a sunken or depressed geological formation
	Synonyms:		depression
	Antonyms:		elevation, natural elevation
	See Also:		basin, bed, bottom, crater, deep, formation, geological formation, geology, hole, hollow, lowland, oceanic abyss, sinkhole, swallow hole, trench, trough, vale, valley