Synonyms for Challenge:

n.

alibi, expert witness, complainant, the accused, aggrieved, provocation, summons, request, the court, appellant, defendant, call. difficulty, dedication, trial, work, effort, hurdle, strain, pursuit, exertion, care, undertaking, heavy lifting, test. interview, put someone on the spot, demand, pick someone's brains, put to. attack, ban, veto, refusal, silence, dismissal. combat, expostulation, squawk, support, kick, protestation, vie, compete, jostle, take on, Remonstration, battle, hold on, exception, remonstrance. disobey, infringe, flout, offend, breach, break, violate. card, the Commonwealth Games, close season, cup, championship, crown, bye, contest. interrogation, rhetorical question, inquiry, questionnaire, leading question. sample, try out, try, crash-test, pilot, put through, put someone/something to the test. challenge (noun)
gainsay, dispute, take exception.
competition (noun)
contest.
confrontation (noun)
engagement.
confutation (noun)
abrogation, invalidation, denial, repudiation, abnegation, rebuttal, rejoinder, refutation, Disaffirmation, confutation, disavowal, contradiction.
counteraction (noun)
neutralization.
disagreement (noun)
complaint, nonagreement, divisiveness, rejection, contention, disunity, argument, disaccord.
dispute, question (noun)
trial, protest, interrogation, dare, defiance, objection, test, remonstrance, demur, confrontation, provocation.
opposition (noun)
obstruction, repression, inhibition, hindrance, disagreement, repulsion, antagonism, opposition, impediment, counteraction, rebuff, interference, defiance, objection, adversary, protest, confrontation, fight, friction, obstinacy, resistance, suppression, counterattack.

v.

communication (verb)
dispute, gainsay.
confront (verb)
encounter, brave, deal with.
counteract (verb)
offset, tamper, neutralize, Counterwork.
defy (verb)
contravene, confront, face, resist, counter, cross, defy, dare, counteract, affront, rebel, countermand, dissent.
disagree (verb)
bicker, argue, object, reject, clash, contend, differ, demur, collide, antagonize, oppose, complain, disagree.
dispute, question (verb)
defy, investigate, confront, cross, brave, inquire, demand, try, query.
oppose (verb)
impede, hinder, repress, suppress, inhibit, meddle, oppress, obstruct, intercept, check, repulse, interfere, repel.
question (verb)
examine, delve, seek, ask, investigate, survey, canvass, debate, poll, interrogate, inquire, interpolate, quiz, catechize, contemplate, probe, question, explore, query.

Other synonyms:

disobey, jostle, alibi, difficulty, complainant, protestation, the Commonwealth Games, heavy lifting, defendant, exertion, vie, crash-test, the accused, flout, expert witness, Remonstration, appellant, refusal. bye, ban, squawk, close season, dedication, infringe, remonstrance, offend, effort, aggrieved, undertaking, expostulation, silence. compete, veto, try out, pursuit, dismissal, provocation, championship, hold on. exception, violate. strain, work, put through, trial, take on. breach, try, battle, kick, care. combat, pilot. sample. cup. test. card, break, crown. disagree
demur.
question
ask.
venture
try out.
Other relevant words:
combat, test, effort, refusal, complainant, call, difficulty, gainsay, flout, compete, squawk, championship, interrogation, contest, crown, leading question, Remonstration, card, take exception, offend, try, protestation, demand, provocation, bye, jostle, battle, remonstrance, cup, attack, disobey, take on, summons, kick, veto, alibi, expostulation, defendant, undertaking, trial, vie, crash-test, dismissal, exception.

Usage examples for challenge

  1. It is otherwise with the Odes et Ballades of 1826, and the Orientales of 1829. Here the Romantic challenge is definitely thrown down. – A Short History of French Literature by George Saintsbury