Challenge
 

challenge
noun1.a demanding or stimulating situation; "they reacted irrationally to the challenge of Russian power"2.a call to engage in a contest or fight3.questioning a statement and demanding an explanation; "his challenge of the assumption that Japan is still our enemy"4.a formal objection to the selection of a particular person as a juror5.a demand by a sentry for a password or identification
verb1.take exception to; "She challenged his claims"2.issue a challenge to; "Fischer challenged Spassky to a match"3.ask for identification; "The illegal immigrant was challenged by the border guard"4.raise a formal objection in a court of law