What is the definition of metamorphic rock?

Metamorphic rock is defined as rock that has undergone transformation due to heat and pressure. This process can change the mineral structure, texture, and overall composition of the original rock, which can be either igneous or sedimentary. During metamorphism, existing minerals can recrystallize, new minerals can form, and the rock can develop foliation or banding due to the alignment of minerals under directional pressure. This transformative process distinguishes metamorphic rocks from other rock types.

In contrast, rock formed from volcanic activity pertains to igneous rocks, while rocks that contain fossils are primarily sedimentary in nature. Additionally, the definition of a rock composed entirely of minerals applies broadly to all types of rocks and does not specifically define metamorphic rocks.