Challenge:

Pronunciation:: \ˈcha-lənj\
Function:: verb
Inflected Form(s):: chal·lenged; chal·leng·ing
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 dispute especially as being unjust, invalid, or outmoded :impugn <new data that challenges old assumptions>
to question formally the legality or legal qualifications of <challenge a juror>
to demand as due or deserved :require <an event that challenges explanation>
to order to halt and prove identity <the sentry challenged the stranger>
to invite into competition <he challenged his brother to a tennis match>
to arouse or stimulate especially by presenting with difficulties <she wants a job that will challenge her>
to administer a physiological and especially an immunologic challenge to (an organism or cell)
to confront or defy boldly :dare <he challenged his critics to prove his guilt>
to call out to duel or combat

intransitive verb
1: to make or present a challenge
2: to take legal exception

— chal·leng·er noun