spleen

1. (anatomy, immunology) In vertebrates, including humans, a ductless vascular gland, located in the left upper abdomen near the stomach, which destroys old red blood cells, removes debris from the bloodstream, acts as a reservoir of blood, and produces lymphocytes.countableuncountable

2. (archaic, except in the set phrase "to vent one's spleen") A bad mood; spitefulness. Compare gall.Examples: "In noble minds some dregs remain, / Not yet purged off, of spleen and sour disdain."; "Too many, however, who might take an honourable stand, fear the petty spleen of the plantocracy; preferring the most disgusting adulation, to the blessing of him ready to perish."; "The name I like best, however, I heard uttered by the Eldest Son of the House of Chou, who in a moment of spleen referred to his colleague of the House of Liang as hsiao chu-tan, the Little Pig’s Egg."archaiccountableuncountable

3. (obsolete, rare) A sudden motion or action; a fit; a freak; a whim.Examples: "A thousand spleens bear her a thousand ways. Brief as the lightning in the collied night; That, in a spleen, unfolds both heaven and Earth"countableobsoleterareuncountable

4. (obsolete) Melancholy; hypochondriacal affections.Examples: "Bodies changed to various forms by spleen."; "There is a luxury in self-dispraise: / And inward self-disparagement affords / To meditative spleen a grateful feast."countableobsoleteuncountable