"fastness" in the noun sense
1. speed, swiftness, fastness
a rate (usually rapid) at which something happens
"the project advanced with gratifying speed"
2. fastness, fixedness, fixity, fixture, secureness
the quality of being fixed in place as by some firm attachment
3. stronghold, fastness
a strongly fortified defensive structure
Source: WordNet® (An amazing lexical database of English)
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