: a stimulating task or problem
- looking for new challenges
: a calling to account or into question : protest
- a challenge to unauthorized use of public funds
: an exception taken to a juror before the juror is sworn
- a challenge of a prospective juror based on a specific cause or reason
: a questioning of the right or validity of a vote or voter
: a sentry's command to halt and prove identity
- The intruder fled at the sentry's challenge.
: an invitation to compete in a sport
- He accepted my challenge to a game of chess.
: a summons (see 1summons 2) that is often threatening, provocative, stimulating, or inciting;
: a summons to a duel to answer an affront
: the act or process of provoking or testing physiological activity by exposure to a specific substance;
: a test of immunity by exposure to an antigen