- The state of being fast and firm; firmness; fixedness;
security; faithfulness. - 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.
Meaning of 'fastness' (Princeton's WordNet)
1 . fastness
[ n]
Meaning (1): - a rate (usually rapid) at which something happens