A deformation is a change in the usual shape of something — especially one that makes it worse — or the process of that change. A dent in a car door is a small deformation. In geology and physics the same word can be cooler and more technical: rocks record deformation from pressure deep in the earth; engineers measure how much a beam deforms. So the tidy “spoiled shape” of everyday English is not the whole story in science, where deformation may be expected, measured, even useful. It is a formal noun. People do not often use it for a person; that is more likely deformity, which is a different, more medical word. You will see it in textbooks, crash reports, and materials science more than in chat.