unyielding

Adjective

• resistant to physical force or pressure
  • an unyielding head support
    

• 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
    

Related words

• Synonyms: 
  dogged , dour , persistent , pertinacious , tenacious