adj. 25B6; adjective DEMANDING, testing, taxing, exacting; stretching, exciting, stimulating, inspiring; difficult, tough, hard, formidable, onerous, arduous, strenuous, gruelling; formal exigent.
easy, uninspiring.
CHALLENGING
Meaning of CHALLENGING in English
Concise Oxford thesaurus English vocabulary. Краткий оксфордский словарь английского языка тезаурус. 2012