paint (a wall, building, or room) with whitewash

the brick walls have been whitewashed

deliberately attempt to conceal unpleasant or incriminating facts about (someone or something)

most sources prefer to ignore or whitewash the most disturbing aspect of such reports

there have been efforts to whitewash the minister's grim record

defeat (an opponent) in every game of a series

Ireland were whitewashed 5-0