#1 toughness n. [stamina, staying power] enduring strength and energy. wn
#2 toughness n. [huskiness, ruggedness] the property of being big and strong. wn
#3 toughness n. [temper] the elasticity and hardness of a metal object; its ability to absorb considerable energy before cracking. wn
#4 toughness n. [formidability] impressive difficulty. wn
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