Adjective has 1 sense

• gruelling(s = adj.all) arduous, backbreaking, grueling, hard, heavy, laborious, operose, punishing, toilsome - characterized by effort to the point of exhaustion; especially physical effort; "a grueling campaign"; "hard labor"; "heavy going"; "heavy work"; "set a punishing pace"; "spent many laborious hours on the project"; "worked their arduous way up the mining valley"