Open English Wordnet
Adjectives
(s)arduous, backbreaking, grueling, gruelling, hard, heavy, laborious, operose, punishing, toilsomecharacterized 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”