Wiktionary
unmalleable
a. Not malleable.
WordNet
unmalleable
adj. difficult or impossible to shape or work
Usage examples of "unmalleable".
The mistress of the house meanwhile, as is usual with persons of her stiff and unmalleable cast, stood mostly aside.
The quality of Hepzibah's mind was too unmalleable to take new impressions so readily as Clifford's.
But she would love to see him and it was a fair compromise with the unmalleable decision of the other boys’ mother.
The trays on which their food had appeared were smooth, unmalleable metal.