unyielding

adjectives

stubbornly unyielding
"dogged persistence"; "dour determination"; "the most vocal and pertinacious of all the critics"; "a mind not gifted to discover truth but tenacious to hold it"- T.S.Eliot; "men tenacious of opinion"
dogged, dour, persistent, pertinacious, tenacious, unyielding
is derived from
unyieldingness
resistant to physical force or pressure
"an unyielding head support"
unyielding
is similar to
resisting weight or pressure
hard