blow someone's cover

Verb

blow someone's cover (third-person singular simple present blows someone's cover, present participle blowing someone's cover, simple past blew someone's cover, past participle blown someone's cover)

1. (idiomatic) To reveal that someone's behavior, situation, or identity has been fabricated or deliberately misrepresented for an ulterior motive.
   • Iskander's role as a G.A.M. operative was secret—until I unwittingly blew his cover that day.2007 February 15, Andrew Marshall, “The Escape Artist”, in Time, retrieved 06 Jul 2015
   • Others have tried to blow his cover: George Galloway, a left-wing British politician and supporter of the Palestinian cause, published Mr. Mahmood’s photo on his website in 2006 and accused Mr. Mahmood of disguising himself as an Arab businessman and trying to entice him to make anti-Semitic...2014 November 19, Katrin Bennhold, “A Tabloid ‘Fake Sheikh,’ Bane of Crooks and Royalty, Finds He’s Now the Story”, in New York Times, retrieved 06 Jul 2015
2. (idiomatic, reflexive) To reveal that one has fabricated or deliberately misrepresented one's own behavior, situation, or identity for an ulterior motive.
   • This spy film purports to be inspired by the true story of Kim Philby (1912-1988), a British intelligence officer and Soviet spy during the 1940s and '50s who gained international notoriety when he blew his cover and defected to the USSR in 1963.1984 August 24, Lawrence Van Gelder, “The Jigsaw Man (1984): Review Summary”, in New York Times, retrieved 06 Jul 2015