Fast"ness, n. [AS. faestnes, fr. faest fast. See Fast, a.]
The state of being fast and firm; firmness; fixedness; security; faithfulness.
All . . . places of fastness [are] laid open.
Sir J. Davies.
A fast place; a stronghold; a fortress or fort; a secure retreat; a castle; as, the enemy retired to their fastnesses in the mountains.
Conciseness of style.
The state of being fast or swift.
© Webster 1913.