To cause to burst forth; to eject; as, to erupt lava.

To eject something, esp. lava, water, etc., as a volcano or geyser; as, when Mount Saint Helens erupted, some people were taken by surprise.

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.

start abruptly; "After 1989, peace broke out in the former East Bloc"

become raw or open; "He broke out in hives"; "My skin breaks out when I eat strawberries"; "Such boils tend to recrudesce"

appear on the skin; "A rash erupted on her arms after she had touched the exotic plant"

To release something that is confined.

as of teeth, for example; "The tooth erupted and had to be extracted"