tough·ness noun (-es) Etymology: Middle English toughnes, from tough (I) + -nes -ness 1.: the quality or state of being tough < had a physical and moral toughness of fibre which enabled him … to endure misfortune — Sir Winston Churchill > 2.: the ability of a metal to absorb considerable energy before fracture 3.: the quality of a paint or coating that causes it to resist chipping, abrasion, or cracking