natural depression(n = noun.object) depression - a sunken or depressed geological formation;
is a kind of formation, geological formation
has particulars: basin, bed, bottom, crater, hole, hollow, lowland, sink, sinkhole, swallow hole, deep, oceanic abyss, trench, trough, vale, valley
Antonym: natural elevation

agitated depression, anaclitic depression, clinical depression, depression, dysthymic depression, endogenous depression, exogenous depression, great depression, involutional depression, manic depression, natural, natural ability, natural action, natural childbirth, natural covering, natural elevation, natural enclosure, natural endowment, natural event, natural family, natural family planning, natural fiber, natural fibre, natural gas, natural glass, natural history, natural immunity, natural language, natural language processing, natural language processing application, natural language processor, natural law, natural logarithm, natural number, natural object, natural order, natural phenomenon, natural philosophy, natural process, natural product, natural product chemistry, natural resin, natural resource, natural resources, natural right, natural rubber, natural science, natural scientist, natural selection, natural shape, natural spring, natural state, natural steel, natural theology, natural virtue, natural world, neurotic depression, psychotic depression, reactive depression, retarded depression, royal society of london for improving natural know, unipolar depression