Eruption \E*rup"tion\, n. [L. eruptio, fr. erumpere, eruptum, to break out; e out + rumpere, to break: cf. F. ['e]ruption. See Rupture.]

1. The act of breaking out or bursting forth; as:
   (a) A violent throwing out of flames, lava, etc., as from a volcano of a fissure in the earth's crust.
   (b) A sudden and overwhelming hostile movement of armed men from one country to another. --Milton.
   (c) A violent commotion.

All Paris was quiet . . . to gather fresh strength for the next day's eruption. --W. Irving.

2. That which bursts forth.

3. A violent exclamation; ejaculation.

He would . . . break out into bitter and passionate eruditions. --Sir H. Wotton.

4. (Med.) The breaking out of pimples, or an efflorescence, as in measles, scarlatina, etc.

Source: Webster's Revised Unabridged Dictionary (1913)