Open English Wordnet
Nouns
(n)challengea demanding or stimulating situation“they reacted irrationally to the challenge of Russian power” (n)challengea call to engage in a contest or fight (n)challengequestioning a statement and demanding an explanation“his challenge of the assumption that Japan is still our enemy” (n)challengea formal objection to the selection of a particular person as a juror (n)challengea demand by a sentry for a password or identification Verbs
(v)challengeissue a challenge to“Fischer challenged Spassky to a match” (v)challengeask for identification“The illegal immigrant was challenged by the border guard”