fastness

noun10

1. •
   The quality or state of being fast (in various senses).
2. •
   A fortified or secure place; a fortress, a stronghold.

   • [I]f the VVelsh compelled by famine ventred out of their strengthes or fastnesses, in or about Snovvdon, the Garrison Souldiers of Gannocke vvere ready to intercept and kill them; […] — 1611
3. •
   The quality or state of being strongly attached; firmness, secureness, tenacity.

   • [T]his is the sure, infallible Test of Love, that the Measure of its Strength is to be taken by the Fastness of its Hold. — 1699
4. •
   The ability of a dye to withstand fading.

   • Although aniline dyes have replaced most natural dyes in the modern era, natural dyers still revere cochineal for its brilliance and fastness. — 2026
5. •
   The quality or state of moving quickly; quickness, rapidity, swiftness.

   • [Frog:] Why are all of us fleein'? What dire peril threatens our sylvan fastness? [Bug:] Just run! Your fastness shouldn't be too slow. — 1959
6. •
   The quality or state of having an extravagant lifestyle or immoral habits.
7. •
   Something that is fast, or that causes someone or something to be fast (in various senses).
8. •
   Something used to fasten or tie; a fastener or fastening.
9. •
   (no longer used) Of a fortress or other place: the quality or state of being secure from access or attack; safety, security.

   • But now his cruelty so sore she drad, / That to those fennes for fastnesse she did fly, / And there her selfe did hyde from his hard tyranny. — 1596
10. •
    (no longer used) The quality or state of being firm, hard, or solid; firmness, hardness, solidity.