shrewd

1. Characterized by keen awareness, sharp intelligence, and often a sense of the practical.

2. Disposed to artful and cunning practices; tricky.

3. Sharp; penetrating: a shrewd wind.

Synonyms: These adjectives mean having or showing keen awareness, sound judgment, and often resourcefulness, especially in practical matters. Shrewd suggests a sharp intelligence, hardheadness, and often an intuitive grasp of practical considerations: "He was too shrewd to go along with them upon a road which could lead only to their overthrow" (J.A. Froude).
Sagacious connotes prudence, discernment, and farsightedness: "He was observant and thoughtful, and given to asking sagacious questions" (John Galt).
Astute suggests shrewdness, especially with regard to one's own interests: An astute tenant always reads the small print in a lease.
Perspicacious implies penetration and clear-sightedness: She is much too perspicacious to be taken in by such a spurious argument. See Also Synonyms at clever.