1. (

• dogged ,
• dour ,
• persistent ,
• pertinacious ,
• tenacious ,
• unyielding

) 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" ;

2. (

• unyielding

) resistant to physical force or pressure; "an unyielding head support" ;