The phrase "most transmutable" refers to something that is highly changeable or malleable. When searching for synonyms for this term, one might consider terms such as adaptable, flexible, mutable, or versatile. These words suggest that the object or concept in question can be easily modified or transformed to suit a variety of different contexts or purposes. Other possible synonyms might include words like pliable, responsive, supple, or fluid, all of which suggest a sense of fluidity or adaptability. By choosing the right synonym, speakers and writers can convey the precise meaning and nuance they intend, and help their audience to understand the full range of possibilities inherent in the object or concept they are discussing.