What is the meaning of arduous?

adjective

• Characterized by effort to the point of exhaustion; especially physical effort.
  • usage: "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"
  • synonyms: backbreaking, grueling, gruelling, hard, heavy, laborious, operose, punishing, toilsome
• Taxing to the utmost; testing powers of endurance."his final, straining burst of speed"; "a strenuous task"; "your willingness after these six arduous days to remain here- F. D. Roosevelt
  • synonyms: straining, strenuous
• Difficult to accomplish; demanding considerable mental effort and skill.
  • usage: "the arduous work of preparing a dictionary"