1 [no object] (of a volcano) become active and eject lava, ash, and gases:Mount Pinatubo began erupting in June be ejected from an active volcano:hot lava erupted from the crust (of an object) explode with fire and noise:smoke bombs erupted everywhere
2break out suddenly and dramatically:fierce fighting erupted between the army and guerrillas noise erupted from the drawing room
3give vent to anger, amusement, etc. in a sudden and noisy way:the soldiers erupted in fits of laughter
4(of a spot, rash, or other mark) suddenly appear on the skin: a boil had erupted on her temple (of the skin) suddenly develop a spot, rash, or mark: his skin erupts with hives
5(of a tooth) break through the gums during normal development: the lower incisors had erupted