Emily Dickinson Lexicon

SPLEEN, n. [L. splen; Gr. σπλην.]

1. The milt; a spungy viscus situated in the left hypochondrium, near the fundus of the stomach, and under the ribs. It has an oval figure. Its use is not known. The ancient supposed this to be the seat of melancholy, anger or vexation. Hence,
2. Anger; latent spite; ill humor. Thus we say to vent one's spleen. In noble minds some dregs remain, / Not yet purged off, of spleen and sour disdain. – Pope.
3. A fit of anger. – Shak.
4. A fit; a sudden motion. [Not used.] – Shak.
5. Melancholy; hypochondriacal affections. Bodies chang'd to recent forms by spleen. – Pope.
6. Immoderate merriment. [Not in use.] – Shak.