challenge verb

1 question whether sth is right/true

ADV. directly The newspaper was directly challenging the government's legitimacy. | seriously | effectively She was effectively challenging the whole basis on which society was run. | successfully The story was completely untrue and was successfully challenged in court.

PREP. on She challenged him on his old-fashioned views.

2 invite sb to compete, argue, etc.

ADV. seriously No one has seriously challenged the champion. | successfully, unsuccessfully

PREP. for She was poised to challenge for the party leadership. | to The count challenged him to a duel.