What is the meaning of challenge?

noun

• A demanding or stimulating situation.
  • usage: "they reacted irrationally to the challenge of Russian power"
• A call to engage in a contest or fight.
• Questioning a statement and demanding an explanation.
  • usage: "his challenge of the assumption that Japan is still our enemy"
• A formal objection to the selection of a particular person as a juror.
• A demand by a sentry for a password or identification.

verb

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