chal·lenge (chăĺənj)

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[Middle English chalenge, from Old French, from Latin calumnia, trickery, false accusation; see calumny, V., from Middle English chalengen, from Old French chalangier, from Latin calumniārī, from calumnia.]

noun 

1. 1. A call to engage in a contest, fight, or competition: a challenge to a duel.
   2. An act or statement of defiance; a call to confrontation: a challenge to the government's authority.
2. A demand for explanation or justification; a calling into question: a challenge to a theory.
3. A sentry's call to an unknown party for proper identification.
4. A test of one's abilities or resources in a demanding but stimulating undertaking: a career that offers a challenge.
5. A claim that a vote is invalid or that a voter is unqualified.
6. Law A formal objection to the inclusion of a prospective juror in a jury.
7. Immunology The induction or evaluation of an immune response in an organism by administration of a specific antigen to which it has been sensitized.

verb: -lenged, -leng·ing, -leng·es. 

transitive verb 

1. 1. To call to engage in a contest, fight, or competition: challenged me to a game of chess.
   2. To invite with defiance; dare: challenged him to contradict her. See synonyms at defy
2. To take exception to; call into question; dispute: a book that challenges established beliefs.
3. To order to halt and be identified, as by a sentry.
4. Law To take formal objection to (a prospective juror).
5. To question the qualifications of (a voter) or validity of (a vote).
6. To have due claim to; call for: events that challenge our attention.
7. To summon to action, effort, or use; stimulate: a problem that challenges the imagination.
8. Immunology To induce or evaluate an immune response in (an organism) by administering a specific antigen to which it has been sensitized.

intransitive verb 

1. To make or give voice to a challenge.
2. To begin barking upon picking up the scent. Used of hunting dogs.

derivatives

chaĺlenge·a·ble

adjective