#1 challenge v. [dispute, gainsay] take exception to; "She challenged his claims". wn
#2 challenge v. issue a challenge to; "Fischer challenged Spassky to a match". wn
#3 challenge n. a demanding or stimulating situation; "they reacted irrationally to the challenge of Russian power". wn
#4 challenge n. a call to engage in a contest or fight. wn
#5 challenge n. questioning a statement and demanding an explanation; "his challenge of the assumption that Japan is still our enemy". wn
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