—n. 1. a call or summons to engage in any contest, as of skill, strength, etc.
2. something that by its nature or character serves as a call to battle, contest, special effort, etc.: Space exploration offers a challenge to humankind. 3. a call to fight, as a battle, a duel, etc.
4. a demand to explain, justify, etc.: a challenge to the treasurer to itemize expenditures. 5. difficulty in a job or undertaking that is stimulating to one engaged in it.
6. Mil.the demand of a sentry for identification or a countersign.
7. Law.a formal objection to the qualifications of a particular juror, to his or her serving, or to the legality of an entire jury. Cf. peremptory challenge. 8. the assertion that a vote is invalid or that a voter is not legally qualified.
9. Biol.the process of inducing or assessing physiological or immunological activity by exposing an organism to a specific substance.
10. Hunting.the crying of a hound on finding a scent.
—v.t. 1. to summon to a contest of skill, strength, etc.
2. to take exception to; call in question: to challenge the wisdom of a procedure. 3. to demand as something due or rightful.
4. Mil.to halt and demand identification or countersign from.
5. Law.to take formal exception to (a juror or jury).
6. to have a claim to; invite; arouse; stimulate: a matter which challenges attention. 7. to assert that (a vote) is invalid.
8. to assert that (a voter) is not qualified to vote.
9. to expose an organism to a specific substance in order to assess its physiological or immunological activity.
10. Archaic.to lay claim to.
—v.i. 1. to make or issue a challenge.
2. Hunting.(of hounds) to cry or give tongue on picking up the scent.
—adj. donated or given by a private, corporate, or government benefactor on condition that the recipient raise an additional specified amount from the public: a challenge grant.