characterized by 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"消耗といっていいほどの努力によって特徴づけられる難しい
例:spent many laborious hours on the project その企画に何時間も骨の折れる時間を費やした