ex·act·ing 
/ɪgˈzæktɪŋ/ adjective
/ɪgˈzæktɪŋ/ adjective [more exacting; most exacting] : requiring much time, attention, or effort from someone : very difficult or demanding
▪ an exacting process/teacher/task ▪ He has very exacting standards/requirements.
▪ an exacting process/teacher/task ▪ He has very exacting standards/requirements.
— ex·act·ing·ly adverb
▪ exactingly high standards
▪ exactingly high standards
