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):

astute
    adj 1: marked by practical hardheaded intelligence; "a smart
           businessman"; "an astute tenant always reads the small
           print in a lease"; "he was too shrewd to go along with
           them on a road that could lead only to their overthrow"
           [syn: astute, sharp, shrewd]

Moby Thesaurus II by Grady Ward, 1.0:

94 Moby Thesaurus words for "astute":
   Machiavellian, Machiavellic, acute, adroit, alert, apperceptive,
   appercipient, arch, argute, artful, cagey, calculating, canny,
   clever, cogent, crafty, cunning, cute, deceitful, deep, deep-laid,
   designing, diplomatic, discerning, discreet, farseeing, farsighted,
   feline, foreseeing, foresighted, forethoughted, forethoughtful,
   foxy, guileful, heady, incisive, ingenious, insidious, insightful,
   intelligent, inventive, judicious, keen, knowing, knowledgeable,
   longheaded, longsighted, observant, pawky, penetrating, perceptive,
   percipient, perspicacious, perspicuous, piercing, politic,
   provident, prudent, quick, quick-witted, ready, resourceful,
   sagacious, sage, savvy, scheming, serpentine, sharp, shifty,
   shrewd, slick, slippery, sly, smooth, snaky, sneaky, sophistical,
   stealthy, strategic, subtile, subtle, supple, tactical, trenchant,
   trickish, tricksy, tricky, underhand, underhanded, understanding,
   vulpine, wary, wily, wise