This is the 5653rd most frequent Japanese word.
しれっと
"しれっと" means "nonchalantly" or "calmly, as if nothing happened."
In this context, 'しれっと' implies nonchalant or casual action, behaving as if nothing was wrong.
彼女はしれっとミーティングに遅れてやってきた。
She casually arrived late to the meeting.
Here, 'しれっと' describes the way the person ignored or disregarded the issue casually, as though it was unimportant.
彼は彼のミスをしれっと受け流した。
He nonchalantly brushed off his mistake.
In this sentence, 'しれっと' suggests an indifferent or unaffected acknowledgment, without emotional response.