eruptv. t.[See eruption.] To cause to burst forth; to eject; as, to erupt lava.(Huxley.)v. i.[See eruption.]1. To eject something, esp. lava, water, etc., as a volcano or geyser; as, when Mount Saint Helens erupted, some people were taken by surprise.()2. To burst forth; to break out, as ashes from a volcano, teeth through the gums, etc.; as, the third molar erupts late in most people, and in some persons does not occur at all.()When the amount and power of the steam is equal to the demand, it erupts with violence through the lava flood and gives us a small volcano. (H. J. W. Dam.)