Challenge

noun

a call to take part in a contest or completion, especially a duel.

synonyms: dare, provocation; summons

an objection or query as to the truth of something, often with an implicit demand for proof.

synonyms: test, questioning, dispute, stand, opposition, confrontation

verb

invite someone to engage in a contest.

dispute the truth or validity of.

synonyms: question, disagree with, dispute, take issue with, protest against, call into question, object to