/ spliːn; NAmE / noun
1.
[ C ] a small organ near the stomach that controls the quality of the blood cells :
a ruptured spleen
—picture at organ
2.
[ U ] ( literary ) anger :
He vented his spleen (= shouted in an angry way) on the assembled crowd.
—see also splenetic
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WORD ORIGIN
Middle English : shortening of Old French esplen , via Latin from Greek splēn ; sense 2 derives from the earlier belief that the spleen was the seat of bad temper.