hahaha, maybe 뷁 is right, It's sort of slang term used by teenagers but not popular anymore. it's originated from English word, 'Break', one of korean singer pronounced 'break' very funny, and people created new slang term to make fun of it,(break브레이크 -> 브렉 -> 부엑 -> 뷁) and it caught popularity a lot, People used to spit that word in annoying situation, or expressing negative feeling,,Actually It's meaningless, it's similar to 'shit'. kkkk where did you find that word? interesting.

Do you mean뷁 ? Haha I never saw 쀩 be4.