noun

• (geology) The process by which rocks are changed into other forms by the application of heat and/or pressure.
• (zoology) The process by which insects develop through life stages, for example, those of embryo, larva, pupa and imago. The life cycle of the butterfly is one of complete metamorphosis, in which the embryo grows within the egg, hatches into the larval stage caterpillar, enters the pupal stage within its chrysalis, and finally emerges as an adult butterfly imago.
• (by extension) Any dramatic change from one thing to another