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. (

• dour ,
• forbidding ,
• grim ,

) harshly uninviting or formidable in manner or appearance; "a dour, self-sacrificing life"; "a forbidding scowl"; "a grim man loving duty more than humanity"; "undoubtedly the grimmest part of him was his iron claw"- J.M.Barrie ;

3. (

• dark ,
• dour ,
• glowering ,
• glum ,
• moody ,
• morose ,
• saturnine ,
• sour ,
• sullen

) showing a brooding ill humor; "a dark scowl"; "the proverbially dour New England Puritan"; "a glum, hopeless shrug"; "he sat in moody silence"; "a morose and unsociable manner"; "a saturnine, almost misanthropic young genius"- Bruce Bliven; "a sour temper"; "a sullen crowd" ;