arduous
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(s) characterized 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
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(s) 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
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(s) difficult to accomplish; demanding considerable mental effort and skill
- the arduous work of preparing a dictionary