definition of
fastness

[1] #1 fastness n. [speed, swiftness] a rate (usually rapid) at which something happens; "the project advanced with gratifying speed". wn

[2] #2 fastness n. [fixedness, fixity, fixture, secureness] the quality of being fixed in place as by some firm attachment. wn

[3] #3 fastness n. [stronghold] a strongly fortified defensive structure. wn