Metamorphic describes something that has been transformed or changed in form, especially through heat, pressure, or other powerful forces.

In geology, metamorphic rocks are rocks that started as one type of rock but changed into something completely different deep underground. Limestone, a soft rock made from ancient sea creatures, can become marble when buried deep in the Earth, where intense heat and pressure squeeze and cook it for millions of years. Shale, made from compressed mud, can transform into slate, the smooth stone once used for chalkboards and roofing. The original rock doesn't melt: it gets rearranged at the molecular level into something new and often much harder.

You might hear it used beyond geology too. A city neighborhood undergoing metamorphic change is being completely transformed, rebuilt from the ground up. When scientists describe a metamorphic process, they mean something that fundamentally restructures what it touches.

The related word metamorphosis describes a dramatic transformation, like when a caterpillar becomes a butterfly. Both words share that sense of deep, thorough change rather than surface-level adjustment.