Impugn

/ɪmˈpjuːn/ verb hard

To attack or cast doubt on someone's honesty, character, or motives, usually through pointed argument.

The lawyer tried to impugn the witness's credibility by highlighting inconsistencies in her story.

Memory Trick

Shares a root with 'pugnacious' (Latin 'pugnare,' to fight) — to impugn someone is to throw a verbal punch at their reputation.