Emily Dickinson Lexicon

DIS-SERT-A'TION, n. [L. dissertatio, from disserto, to discourse, from dissero, id.; dis and sero, to sow, that is, to throw. Dissero is, to throw out, to cast abroad.]

1. A discourse, or rather a formal discourse, intended to illustrate a subject.
2. A written essay, treatise or disquisition; as, Plutarch's dissertation on the poets; Newton's dissertations on the prophecies.