Rapidness of movement or activity
Vibrations increase in rapidity as a note rises and decrease as it falls.
She wrote with the rapidity of Walter Scott and the regularity of Anthony Trollope.
She can add and subtract with great rapidity up to the sum of one hundred; and she knows the multiplication tables as far as the FIVES.
The rapidity of the Russian pursuit was just as destructive to our army as the flight of the French was to theirs.
In this way a train is distributed with great rapidity, especially if the points giving access to the different sidings are worked by power so that they can be quickly manipulated.