arduous

Meanings

• characterized by effort to the point of exhaustion; especially physical effort
  • "worked their arduous way up the mining valley"
• taxing to the utmost; testing powers of endurance; ; ; - F.D.Roosevelt
  • "your willingness after these six arduous days to remain here"
• difficult to accomplish; demanding considerable mental effort and skill
  • "the arduous work of preparing a dictionary"

Synonyms

backbreaking, grueling, gruelling, hard, heavy, laborious, operose, punishing, straining, strenuous, toilsome