F'ASTNESS, noun 1. The state of being fast and firm; firm adherence. 2. Strength; security. The places of fastness are laid open. 3. A strong hold; a fortress or fort; a place fortified; a castle. The enemy retired to their fastnesses. 4. Closeness; conciseness of style. [Not used.]
Source: Webster's 1828 American Dictionary ↗ · public-domain · returned verbatim, no AI