Proteiform is a word that describes something which can change its shape, form, or appearance. Synonyms for this word include mutable, versatile, adaptable, variable, and transformable. Other similar words could be pliable, malleable, fluid, supple, or plastic. These terms all describe something that is able to change or take on different forms easily. Proteiform also implies a great deal of flexibility and variability, so words like versatile and adaptable are particularly fitting. Overall, there are many synonyms for proteiform which capture the sense of shape-shifting or transformation that the word implies.