Merriam-Webster's Collegiate® Dictionary, 11th Edition
CHALLENGE
I. verb (challenged; challenging)
Etymology: Middle English chalengen to accuse, from Anglo-French chalenger, from Latin calumniari to accuse falsely, from calumnia calumny
Date: 13th century
transitive verb to demand as due or deserved ; require , to order to halt and prove identity , to dispute especially as being unjust, invalid, or outmoded ; impugn , to question formally the legality or legal qualifications of ,
5. to confront or defy boldly ; dare , to call out to duel or combat, to invite into competition , to arouse or stimulate especially by presenting with difficulties , to administer a physiological and especially an immunologic challenge to (an organism or cell), intransitive verb to make or present a challenge, to take legal exception, challenger noun
II. noun
Date: 14th century
1. a summons that is often threatening, provocative, stimulating, or inciting, an invitation to compete in a sport,
2. a calling to account or into question ; protest , an exception taken to a juror before the juror is sworn, a sentry's command to halt and prove identity, a questioning of the right or validity of a vote or voter, a stimulating task or problem , the act or process of provoking or testing physiological activity by exposure to a specific substance