noun

1. a depressing or being depressed
2. a depressed part or place; hollow or low place on a surface
3. low spirits; gloominess; dejection; sadness
4. a decrease in force, activity, amount, etc.
5. Astron. the angular distance of a celestial body below the horizon
6. ☆ Econ. a period marked by slackening of business activity, widespread unemployment, falling prices and wages, etc.
7. Med. a decrease in functional activity
8. Meteorol.
   1. a lowering of the atmospheric pressure indicated by the fall of mercury in a barometer
   2. an area of relatively low barometric pressure; low
9. Psychol. an emotional condition, either neurotic or psychotic, characterized by feelings of hopelessness, inadequacy, etc.
10. Surveying the angular distance of an object below the horizontal plane

Etymology: ME depressioun < OFr depression < L depressio: see depress