difficult to accomplish; demanding considerable mental effort and skill; "the arduous work of preparing a dictionary"
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"
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
marked by imagination, initiative, and readiness to undertake new projects; "an enterprising foreign policy"; "an enterprising young man likely to go far"
showing sustained enthusiastic action with unflagging vitality; "an indefatigable advocate of equal rights"; "a tireless worker"; "unflagging pursuit of excellence"
having a cheerful, lively, and self-confident air; "looking chipper, like a man...diverted by his own wit"- Frances G. Patton; "life that is gay, brisk, and debonair"- H.M.Reynolds; "walked with a jaunty step"; "a jaunty optimist"