cat that ate the canary

/K AE1 T DH AE0 T EY0 T DH AH0 K AH0 N EH0 R IY0/
noun
  1. 1

    (idiomatic) A person who appears self-satisfied or smug, especially while concealing something mischievous, prohibited, or private.

  2. 2

    (idiomatic) A person whose appearance and behavior suggest guilt mixed with other qualities, such as satisfaction or feigned nonchalance.