flinty grim hard-nosed harsh rigid steely strict tough ascetic astringent bitter forbidding rough austere bullheaded by the book cruel disciplinary dyed-in-the-wool frowning hang-tough hard hard-boiled hard-core hard-line hard-shell hardheaded implacable inexorable inflexible mortified mulish relentless rigorous severe stiff-necked stubborn unrelenting unsparing unyielding