inflexible (adj.)
- adamant
- adamantine
- cast-iron
- certain
- changeless
- constant
- determinate
- determined
- dogged
- dour
- dyed
- established
- fated
- fateful
- firm
- fixed
- flinty
- frozen
- fundamentalist
- grim
- hard
- hard-core
- hard-line
- headstrong
- hidebound
- immobile
- immotile
- immovable
- immutable
- impervious
- implacable
- inalterable
- indefeasible
- indomitable
- inelastic
- ineluctable
- inescapable
- inevitable
- inexorable
- inextensible
- intractable
- intransigent
- invariable
- invincible
- iron
- ironclad
- irreconcilable
- irremovable
- irresistible
- irrevocable
- loyal
- mulish
- muscle-bound
- necessary
- obdurate
- obstinate
- orthodox
- pat
- pigheaded
- procrustean
- puritanic
- refractory
- relentless
- resistless
- resolute
- resolved
- rigid
- rigorous
- rock-ribbed
- rockbound
- set
- settled
- severe
- single-minded
- standpat
- stationary
- staunch
- steadfast
- steady
- steely
- stern
- stiff
- stony
- straightlaced
- straitlaced
- strict
- stubborn
- sure
- true
- unaccommodating
- unadaptable
- unaffected
- unalterable
- unavoidable
- unbending
- unchangeable
- unchanging
- uncompromising
- unconquerable
- uncontrollable
- unflappable
- unimpressionable
- unmalleable
- unmodifiable
- unmovable
- unmoved
- unmoving
- unpersuadable
- unpreventable
- unreceptive
- unrelenting
- unresponsive
- unshakable
- unshaken
- unstoppable
- unsusceptible
- unswerving
- unvaried
- unvarying
- unyielding
Zealous, yet modest; innocent, though free;
Patient of toil, serene amidst alarms;
Inflexible in faith, invincible in arms.
