[adjective] characterized by toilsome effort to the point of exhaustion; especially physical effort; "worked their arduous way up the mining valley"; "a grueling campaign"; "hard labor"; "heavy work"; "heavy going"; "spent many laborious hours on the project"; "set a punishing pace" Synonyms:backbreaking, grueling, gruelling, hard, heavy, laborious, punishing, toilsome
[adjective] taxing to the utmost; testing powers of endurance; "his final, straining burst of speed"; "a strenuous task"; "your willingness after these six arduous days to remain here"- F.D.Roosevelt Synonyms:straining, strenuous
[adjective] difficult to accomplish; demanding considerable mental effort and skill; "the arduous work of preparing a dictionary"
