the cat that swallowed the canary meaning
cat that ate the canary. ( 1 idiomatic) A person who appears self-satisfied or smug, especially while concealing something mischievous, prohibited, or private.2  1910, Cotton Bulls Stand Shock of Deliveries, New York Times, 30 Apr., p. 2,aley said that Tietjen, who lives in Middle Island, had the  cat who ate the canary  look when he was pulled over. The 32-year-old driver was apologetic, and never tried to dispute the ticket.