보란 듯이 (bo-ran deu-si) – boastfully/proudly
This phrase has the same meaning as “showing off” in English.
보란 듯이 is basically an adverb that can be used to express how someone is boasting or being very proud of something to show off to others.
형은 어렸을 때 장난감을 바란 듯이 친구에게 자랑해서 좀 짜증났어.
When my elder brother was young, he showed off his toys to his friends so it was annoying.
그 아줌마는 어떤 사람을 만날 때도 자신의 보석류들을 보란 듯이 해서 많이 사람들이 아줌마를 좋아하지 않아.
That Ahjumma shows off her jewellery to every person she meets so many people dislike her.