Fāst'ness, n.

n. [A-S. fāstnes, from fāst. See FAST, a.] 1. The state of being fast and firm; firmness; fixedness; security; faithfulness. The places of fastness are laid open. Davies.

2. A fast place; a stronghold; a fortress or fort; a place fortified; a castle; as, the enemy retired to their fastnesses.
3. Conciseness of style. [Obs.] Ascham.