Synonyms:
- adamant,
- adamantine,
- cast-iron,
- close,
- dour,
- firm,
- flinty,
- grim,
- hard,
- hard-core,
- immovable,
- immutable,
- implacable,
- impliable,
- inductile,
- inelastic,
- inexorable,
- inextensible,
- inextensile,
- inextensional,
- inflexible,
- intractable,
- intractile,
- intransigent,
- iron,
- irreconcilable,
- irresilient,
- mean,
- miserly,
- niggardly,
- nonelastic,
- nonstretchable,
- parsimonious,
- penurious,
- relentless,
- rigid,
- rigorous,
- rock-ribbed,
- save-all,
- steely,
- stern,
- stiff,
- stubborn,
- tight,
- tightfisted,
- unaffected,
- unalterable,
- unbending,
- unchangeable,
- uncompromising,
- unextendible,
- unextensible,
- unflexible,
- unlimber,
- unmalleable,
- unmoved,
- unpliable,
- unpliant,
- unrelenting,
- untractable,
- unyielding