"Impugn" is a transitive verb meaning to cast doubt upon or to challenge or attack as false. The following sentences provide examples of its use: Don't you dare try to impugn my credentials. The...
I would be deeply offended if you were to impugn my honesty.
Teens often impugn the restrictions put on them, like curfews and chores.
Simple past & past participle - impugned Present participle - impugning
I impugned him by providing evidence against him with witnesses