depression

Etymology

From Middle English depression, depressioun, from Old French depression, from Latin dēpressiō.

noun

1. (psychology, usually uncountable) A state of mind producing serious, long-term lowering of enjoyment of life or inability to visualize a happy future.
   I used to suffer from depression, but now I'm mostly content with my life.
   It is that Mr. Levi's death could not be dissociated from the major depression with which he was afflicted, and that indeed his suicide proceeded directly from that illness. 1988-12-19, William Styron, “Why Primo Levi Need Not Have Died”, in The New York Times, →ISSN
2. (psychology, countable) A period of low morale or unhappiness (a period of experiencing the above-mentioned state of mind) which lasts longer than several weeks and may include ideation of self-inflicted injury or suicide.
   […] your illness reflects the textbook description of bipolar disorder (euphoric, grandiose, manic highs followed by deep depressions,[…] 2011-02-28, David J. Miklowitz, The Bipolar Disorder Survival Guide, Second Edition: What You and Your Family Need to Know, Guilford Press, page 106
   His first major breakdown occurred when his son was five years old; he continued to go to pieces periodically, with a particularly deep depression that lasted from the time Bill was in sixth grade until the time he finished junior high[…] 2014-09-16, Andrew Solomon, The Noonday Demon: An Atlas Of Depression, Simon and Schuster, page 73
   Many alcoholics who die from suicide suffer from deep depressions that are quite frequently protracted,[…] 2016-01-14, Danuta Wasserman, Suicide: An unnecessary death, Oxford University Press
3. (geography) An area that is lower in topography than its surroundings.
4. (meteorology) An area of lowered air pressure that generally brings moist weather, sometimes promoting hurricanes and tornadoes.
5. (economics) A period of major economic contraction.
6. (economics, US) Four consecutive quarters of negative, real GDP growth. See NBER.
   The Great Depression was the worst financial event in US history.
7. The act of lowering or pressing something down.
   Depression of the lever starts the machine.
8. (biology, physiology) A lowering, in particular a reduction in a particular biological variable or the function of an organ, in contrast to elevation.