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

• horse nettle
• horse of the wood
• horse opera
• horse parsley
• horse racing
• horse sense
• horse thistle
• horse tick
• horse trader
• horse trading
• horse wrangler
• horse's foot
• horse-and-buggy
• horse-cart
• horse-chestnut family
• horse-drawn
• horse-drawn vehicle
• horse-pistol
• horse-race
• horse-trade
• horse-trail
• horseback
• horseback rider
• horseback riding
• horsebean