1. the quality or state of being fast, firm, or secure
2. a secure or fortified place; a stronghold
3. the resistance of a dye or color to fading or running
Usage: technical

Examples

• The fastness of the knot ensured the rope would not slip.
• The mountain fastness provided refuge for the rebels.
• The ancient castle served as a fastness against invading armies.
• We tested the color fastness of the fabric before washing.
• The fastness of her grip on the railing kept her from falling.
• Pirates used the island as a natural fastness from naval forces.
• The dye’s fastness was excellent, showing no signs of fading after months.