Example: They reacted irrationally to the challenge of Russian power.
source: wordnet30
a call to engage in a contest or fight(noun.communication)
source: wordnet30
questioning a statement and demanding an explanation(noun.communication)
Example: His challenge of the assumption that Japan is still our enemy.
source: wordnet30
a formal objection to the selection of a particular person as a juror(noun.communication)
source: wordnet30
a demand by a sentry for a password or identification(noun.communication)
source: wordnet30
An invitation to engage in a contest or controversy of any kind; a defiance; specifically, a summons to fight a duel; also, the letter or message conveying the summons.(noun)