What is the meaning of decisive?

adjective

• Determining or having the power to determine an outcome.
  • usage: "cast the decisive vote"; "two factors had a decisive influence"
• Unmistakable.
  • usage: "had a decisive lead in the polls"
• Characterized by decision and firmness.
  • usage: "an able and decisive young woman"; "we needed decisive leadership"; "she gave him a decisive answer"
• Forming or having the nature of a turning point or crisis.
  • usage: "a critical point in the campaign"; "the critical test"
  • synonyms: critical