From Longman Dictionary of Contemporary Englishunmaskun‧mask /ʌnˈmɑːsk $ -ˈmæsk/ verb [transitive] FIND OUTto make known the hidden truth about someone He was one of the most high-ranking spies ever unmasked by the CIA.→ See Verb table
Examples from the Corpus
unmask• As glucose concentration falls, severe volume depletion may be unmasked.• It is also through observation that fakes are unmasked.• Perhaps we're in the middle of a nest of spies whom Meredith-Lee was about to unmask.• She needn't have worried about Lori being unmasked.• He was said to be one of the highest-placed spies unmasked by Soviet intelligence in recent years.• And surely J.H. Hodges should have been unmasked earlier.• Only by unmasking the killer can she hope to free herself from the terror.• The CIA succeeded in unmasking the spy who sold military secrets. 