challenge
1. chal.lenge \'chal-*nj\ vb [ME chalengen to accuse, fr. OF chalengier, fr. L calumniari]to accuse falsely, fr. calumnia calumny 1: to demand as of right : REQUIRE of a sentry 2: HALT 3: to take exception to : DISPUTE 4: to question the legality or legal qualifications of 5a: DARE, DEFY 5b: to call out to duel or combat 5c: to invite into competition 1: to make or present a challenge 2: to take legal exception - chal.leng.er n 2. challenge n 1a: a calling to account or into question : PROTEST 1b: an exception taken to a juror before he is sworn 1c: a sentry's command to halt and prove identity 1d: a questioning of the right or validity of a vote or voter 2a: a summons often threatening, provocative, stimulating, or inciting; specif : a summons to a duel to answer an affront 2b: an invitation to compete in a sport 3: a test of immunity by exposure to virulent infective material after spec ific immunization
Webster's English Dictionary