Emily Dickinson Lexicon

E-RUP'TION, [L. eruptio, from erumpo, erupi; e and rumpo, for rupo; Sp. romper; Fr. rompre. See Class Rb, No. 26, 27, 29.]

1. The act of breaking or bursting forth from inclosure or confinement; a violent emission of any thing, particularly of flames and lava from a volcano. The eruptions of Hecla in 1783, were extraordinary for the quantity of lava discharged.
2. A sudden or violent rushing forth of men or troops for invasion; sudden excursion. Incensed at such eruption bold. Milton.
3. A burst of voice; violent exclamation. [Little used.] South.
4. In medical science, a breaking out of humors, a copious excretion of humors on the skin, as in pustules; also, an efflorescence or redness on the skin, as in scarlatina; exanthemata; petechiæ; vibices; as in small pox, measles and fevers.