The word "unmoldable" refers to something that cannot be easily shaped or molded. Some synonyms for this word include inflexible, rigid, unyielding, stiff, unbending, and unadaptable. These words can be used to describe objects or even people who are resistant to change or have a fixed mindset. Other synonyms that convey a similar idea include intractable, unalterable, stubborn, and immutable. These words have a negative connotation and can imply that the subject is difficult to work with or cannot be manipulated. Overall, the use of synonyms can help to convey a more nuanced meaning and add variety to writing.