1. Enduring strength and energy
   "lacking in toughness";
   - stamina, staying power, stickability [informal]
    
2. The property of being big and strong
   "The toughness of the old leather boots was impressive";
   - huskiness, ruggedness
    
3. The elasticity and hardness of a metal object; its ability to absorb considerable energy before cracking
   "The toughness of the new alloy made it ideal for industrial applications";
   - temper
    
4. Impressive difficulty
   "The toughness of the challenge only motivated them to work harder";
   - formidability

Type of: difficultness, difficulty, elasticity, endurance, snap, strength

Encyclopedia: Toughness