whitewash

Concise Oxford English Dictionary © 2008 Oxford University Press:
whitewash/ˈwʌɪtwɒʃ/

▶noun

• 1 a solution of lime and water or of whiting, size, and water, used for painting walls white.

• 2 a deliberate concealment of someone's mistakes or faults.

• 3 informal a victory by the same side in every game of a series.

▶verb

• 1 paint with whitewash.

• 2 conceal (mistakes or faults).

• 3 informal defeat with a whitewash.

– derivatives
whitewashed adjective,
whitewasher noun.