eruptive

adjective

1. bursting forth, or tending to burst forth.
2. pertaining to or of the nature of an eruption.
3. Geology. noting a rock formed by the eruption of molten material.
4. Pathology. causing or accompanied by an eruption or rash.

noun

5. Geology. an eruptive rock.

adjective

1. erupting or tending to erupt
2. resembling or of the nature of an eruption
3. (of rocks) formed from such products as ash and lava resulting from volcanic eruptions
4. (of a disease) characterized by skin eruptions

adj.

1640s; see erupt + -ive. Perhaps from French éruptif.