"the process of changing form or structure," 1837, from metamorphic + -ism. Specifically, in geology, chemical change and rearrangement of the constituents of rock by which they assume new forms and combinations.
1833 (Lyell) in the geological sense, "exhibiting change in form or structure," in reference to rock whose form has been changed by heat or pressure, from Greek meta "trans-" (see meta-) + morphē "form," a word of uncertain origin. Earlier (1816) in a theological sense, "characterized by change of form," from metamorphosis + -ic.
word-forming element making nouns implying a practice, system, doctrine, etc., from French -isme or directly from Latin -isma, -ismus (source also of Italian, Spanish -ismo, Dutch, German -ismus), from Greek -ismos, noun ending signifying the practice or teaching of a thing, from the stem of verbs in -izein, a verb-forming element denoting the doing of the noun or adjective to which it is attached. For distinction of use, see -ity. The related Greek suffix -isma(t)- affects some forms.
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Definitions of metamorphism from WordNet
change in the structure of rock by natural agencies such as pressure or heat or introduction of new chemical substances;