rigorous Synonyms

strict harsh inflexible severe stern tight stiff unyielding stringent scrupulous rigid exact painstaking austere rigorist spartan tighter punctilious strenuous proper punctual ramrod sound sedulous religious restringing scientific rugged precise stringency grueling gruelling dead set pinpoint unpermissive on the button right on unstoppable straitlaced unadaptable taxing veridical carful thorough thoroughgoing throughly tough uncompromising unerring unsparing