Source : Webster's Revised Unabridged Dictionary (1913)

Acuity \A*cu"i*ty\, n. [LL. acuitas: cf. F. acuit['e].]
   Sharpness or acuteness, as of a needle, wit, etc.

Source : WordNet®

acuity
     n 1: sharpness of vision; the visual ability to resolve fine
          detail (usually measured by a Snellen chart) [syn: {visual
          acuity}, {sharp-sightedness}]
     2: a quick and penetrating intelligence; "he argued with great
        acuteness"; "I admired the keenness of his mind" [syn: {acuteness},
         {sharpness}, {keenness}]