toughness

(mechanics) A property of a material capable of absorbing energy by plastic deformation; intermediate between softness and brittleness.

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noun

1. The fact or condition of being rigorous and unsparing: austerity, hardness, harshness, rigidity, rigor, rigorousness, severity, sternness, strictness, stringency. See easy/hard.
2. Unwavering firmness of character, action, or will: decidedness, decision, decisiveness, determination, firmness, purpose, purposefulness, resoluteness, resolution, resolve, will, willpower. See certain/uncertain, strong/weak.

For a material, its ability to absorb energy.