The Collaborative International Dictionary of English v.0.48:

Astute \As*tute"\, a. [L. astutus, fr. astus craft, cunning;
   perh. cognate with E. acute.]
   Critically discerning; sagacious; shrewd; subtle; crafty.
   [1913 Webster]

   Syn: Keen; eagle-eyed; penetrating; skilled; discriminating;
        cunning; sagacious; subtle; wily; crafty.
        [1913 Webster] As*tute"ly, adv. -- As*tute"ness, n.
        [1913 Webster]

WordNet (r) 3.0 (2006):

astuteness
    n 1: intelligence manifested by being astute (as in business
         dealings) [syn: shrewdness, astuteness, perspicacity,
         perspicaciousness]
    2: the intellectual ability to penetrate deeply into ideas [syn:
       astuteness, profundity, profoundness, depth,
       deepness]