1. Characterized by effort to the point of exhaustion; especially physical effort
   - arduous, backbreaking, grueling [US], gruelling [Brit, Cdn], hard, heavy, laborious, punishing, toilsome

See also: effortful, operoseness

• color TV
• color TV tube
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• color vision deficiency
• color wash
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• color-blind
• color-blind person
• color-magnitude diagram
• Coloradan
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• Colorado
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• colorant
• coloration