Noah Webster's Dictionary 1. (n.) The state of being fast and firm; firmness; fixedness; security; faithfulness. 2. (n.) A fast place; a stronghold; a fortress or fort; a secure retreat; a castle; as, the enemy retired to their fastnesses in the mountains. 3. (a.) Conciseness of style. 4. (n.) The state of being fast or swift.

Multi-Version Concordance Fastness (1 Occurrence) Job 39:28 He inhabiteth the rock and maketh his dwelling on the point of the cliff, and the fastness: (DBY RSV)