depression

noun

• 1 [mass noun] severe, typically prolonged, feelings of despondency and dejection: self-doubt creeps in and that swiftly turns to depression
• Medicine a mental condition characterized by severe feelings of hopelessness and inadequacy, typically accompanied by a lack of energy and interest in life:she suffered from clinical depression

• 2a long and severe recession in an economy or market:the depression in the housing market
• (the Depression or the Great Depression) the financial and industrial slump of 1929 and subsequent years.

• 3 [mass noun] the action of lowering something or pressing something down:depression of the plunger delivers two units of insulin
• [count noun] a sunken place or hollow on a surface:the original shallow depressions were slowly converted to creeks

• 4 Meteorology a region of lower atmospheric pressure, especially a cyclonic weather system: hurricanes start off as loose regions of bad weather known as tropical depressions

• 5 Astronomy & Geography the angular distance of an object below the horizon or a horizontal plane.