1. A change in a rock mass caused by the intrusion of external igneous material; in the usual sense, contact metamorphism.

Metamorphism is a process of change in the physical structure of rock as a result of long-term heat and pressure, especially a change that increases the rock's hardness and crystalline structure

2. In petrography, that variety of contact-metamorphism which is developed, in the surrounding walls, by an intruded mass of eruptive rock.