challenge

noun
  1. A call to take part in a contest or competition, especially a duel. noun
    He accepted the challenge to a chess match.
    The knight issued a challenge to his rival.
  2. A task or situation that tests someone's abilities. noun
    Climbing Mount Everest is a significant challenge.
    The project presented a challenge to the entire team.
  3. An objection or query as to the truth of something, often with an implicit demand for proof. noun
    The lawyer raised a challenge to the witness's testimony.
    There was a challenge to the validity of the election results.
  4. To invite someone to engage in a contest. verb
    She challenged him to a race.
    They challenged the other team to a rematch.
  5. To dispute the truth or validity of something. verb
    The scientist challenged the traditional theories.
    He challenged the decision in court.