The Collaborative International Dictionary of English v.0.48:

Perspicacity \Per`spi*cac"i*ty\
   (p[~e]r`sp[i^]*k[a^]s"[i^]*t[y^]), n. [L. perspicacitas: cf.
   F. perspicacit['e]. See Perspicacious.]
   The state of being perspicacious; acuteness of sight or of
   intelligence; acute discernment. --Sir T. Browne.
   [1913 Webster]

WordNet (r) 3.0 (2006):

perspicacity
    n 1: intelligence manifested by being astute (as in business
         dealings) [syn: shrewdness, astuteness, perspicacity,
         perspicaciousness]
    2: the capacity to assess situations or circumstances shrewdly
       and to draw sound conclusions [syn: judgment, judgement,
       sound judgment, sound judgement, perspicacity]

Moby Thesaurus II by Grady Ward, 1.0:

70 Moby Thesaurus words for "perspicacity":
   acuity, acumen, acuteness, apperception, astuteness, clear sight,
   cogency, color vision, cone vision, critical discernment,
   day vision, daylight vision, discernment, discrimination, eye,
   eye-mindedness, eyesight, farseeingness, farsight, farsightedness,
   field of view, field of vision, flair, foresight, foresightedness,
   horizon, incisiveness, insight, judgment, keen sight, keenness,
   ken, longheadedness, longsightedness, night vision, penetration,
   perception, perceptiveness, percipience, peripheral field,
   peripheral vision, perspicaciousness, perspicuity, perspicuousness,
   photopia, power of sight, providence, purview, quick sight, range,
   rod vision, sagaciousness, sagacity, scope, scotopia, seeing,
   sense of sight, sensibility, shrewdness, sight, sightedness, sweep,
   trenchancy, twilight vision, unobstructed vision, vision,
   visual acuity, visual field, visual sense, wit