Definition of: depression

(di·presh′ən) noun
1. The act of depressing, or the state of being depressed; low spirits or vitality; dejection; melancholy.
2. That which is depressed; a low or hollow place.
3. A decline in business or trade; also, the period of time during which this inactivity prevails.
4. Meteorol. Low atmospheric pressure; also, a region of low atmospheric pressure.
5. Astron. The vertical angular distance of a heavenly body below the horizon: opposed to altitude.
6. The angular distance of an object below the horizontal plane through the point of observation: the opposite of elevation.
7. Psychiatry A lowering of vital powers; melancholy; especially, psychopathic melancholy leading to mental disorders.
8. Music Flatting of a tone.