arduous arduous /ˈɑːrdʒuːəs/

adjective

1. () Characterized by effort to the point of exhaustion; especially physical effort  ( backbreaking , grueling [American] , gruelling [Canadian, British] , arduous , heavy , laborious , operose , punishing , toilsome , hard )
   characterized by effort to the point of exhaustion; especially physical effort
    Worked their arduous way up the mining valley
   worked their arduous way up the mining valley
    A grueling campaign
   a grueling campaign
    Hard labor
   hard labor
    Heavy work
   heavy work
    Heavy going
   heavy going
    Spent many laborious hours on the project
   spent many laborious hours on the project
    Set a punishing pace
   set a punishing pace
   
2. Difficult to accomplish; demanding considerable mental effort and skill  ( arduous )
   difficult to accomplish; demanding considerable mental effort and skill
    The arduous work of preparing a dictionary
   the arduous work of preparing a dictionary
   
3. Taxing to the utmost; testing powers of endurance  ( arduous , strenuous , straining )
   taxing to the utmost; testing powers of endurance
    His final, straining burst of speed
   his final, straining burst of speed
    A strenuous task
   a strenuous task
    Your willingness after these six arduous days to remain here
   your willingness after these six arduous days to remain here