しれっと

adverb, noun or participle which takes 'suru'

nonchalantly; calmly; as if nothing happened

Describes acting casually or unfazed, often when one should feel embarrassed, guilty, or surprised. Can imply a slightly cheeky or shameless attitude.

See also: けろっと

• 彼かれは遅ち刻こくしたのに、しれっと会かい議ぎに参さん加かした。

  Even though he was late, he joined the meeting as if nothing had happened.

• 失しっ敗ぱいをしれっとごまかそうとした。

  He tried to nonchalantly cover up his mistake.