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.-that which bursts forth.-a violent exclamation; ejaculation.-the breaking out of pimples, or an efflorescence, as in measles, scarlatina, etc.