The Collaborative International Dictionary of English v.0.48:

Nimbleness \Nim"ble*ness\, n.
   The quality of being nimble; lightness and quickness in
   motion; agility; swiftness.
   [1913 Webster]

WordNet (r) 3.0 (2006):

nimbleness
    n 1: intelligence as revealed by quickness and alertness of
         mind; "nimbleness of wit and imagination" [syn:
         nimbleness, mental dexterity]
    2: the gracefulness of a person or animal that is quick and
       nimble [syn: agility, legerity, lightness,
       lightsomeness, nimbleness]

Moby Thesaurus II by Grady Ward, 1.0:

57 Moby Thesaurus words for "nimbleness":
   acuity, acuteness, adroitness, agility, alacrity, alertness,
   aptitude, aptness, attention, attentiveness, braininess,
   brightness, brilliance, briskness, clear thinking, cleverness,
   dexterity, dispatch, esprit, expedition, expeditiousness,
   featliness, flair, genius, giftedness, gifts, keen-wittedness,
   keenness, lightness, mental alertness, mercurial mind,
   native cleverness, nimble mind, nimble-wittedness, nous,
   promptitude, promptness, punctuality, quick parts, quick thinking,
   quick wit, quick-wittedness, quickness, readiness, ready wit,
   savvy, sharp-wittedness, sharpness, sleeplessness, smartness,
   smarts, speediness, sprightly wit, spryness, swiftness, talent,
   wakefulness