What is the meaning of challenging?

verb

• Take exception to.
  • usage: "She challenged his claims"
  • synonyms: challenge, dispute, gainsay
• Issue a challenge to.
  • usage: "Fischer challenged Spassky to a match"
  • synonyms: challenge
• Ask for identification.
  • usage: "The illegal immigrant was challenged by the border guard"
  • synonyms: challenge
• Raise a formal objection in a court of law.
  • synonyms: challenge, take exception

adjective

• Requiring full use of your abilities or resources.
  • usage: "ambitious schedule"; "performed the most challenging task without a mistake"
  • synonyms: ambitious
• Stimulating interest or thought.
  • usage: "a challenging hypothesis"; "a thought-provoking book"
  • synonyms: thought-provoking
• Disturbingly provocative.
  • usage: "an intriguing smile"
  • synonyms: intriguing