inflexible
in-flex-i-ble
adjective
Unable to bend or be bent easily; stiff and rigid.
"The old pipe was inflexible."
adjective
Unwilling to change or compromise; stubborn or unyielding.
"Her boss was inflexible about deadlines."
Thesaurus
Synonyms: hard-line, uncompromising, sturdy, hardline, unadaptable, rigid, unbending, stiff, semirigid, muscle-bound, intransigent, ossified
Antonyms: compromising, conciliatory, flexible, flexile