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

See also: effortful

• Didelphis virginiana
• dideoxycytosine
• dideoxyinosine
• Diderot
• didgeridoo
• Didion
• didn't
• dido
• Didrikson
• didst
• didymium
• die
• die away
• die down
• die off
• die out
• die-cast
• dieback
• Dieffenbachia
• Dieffenbachia sequine
• diegesis
• Diego Rivera
• Diego Rodriguez de Silva y Velazquez
• Diegueno
• diehard