grueling(s = adj.all) arduous, backbreaking, gruelling, hard, heavy, laborious, operose, punishing, toilsome - 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"

   characterized by toilsome effort; requiring extreme physical or mental effort; as, a grueling campaign. [WordNet 1.5]