shrewd

Adjective

• used of persons
  • the most calculating and selfish men in the community
    

• 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
    

Related words

• Synonyms: 
  calculating , calculative , conniving , scheming , astute , sharp