'Fleetness' definitions:

Definition of 'fleetness'

From: WordNet
noun
Rapidity of movement; "fleetness of foot"

Definition of 'Fleetness'

From: GCIDE
  • Fleetness \Fleet"ness\, n. Swiftness; rapidity; velocity; celerity; speed; as, the fleetness of a horse or of time. [1913 Webster]