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
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