1. What does it mean?
Short for 꾸민 듯 안 꾸민 듯하다, roughly “looking put-together without looking like you tried too hard.” It usually describes clothes, hair, or makeup that look relaxed even though some thought went into them.
2. The nuance
Usually a compliment about an effortless-looking style. It does not literally mean the person made no effort.
3. Examples
“오늘은 꾸안꾸로 입었는데 생각보다 마음에 들어.”
I went for an effortless look today, and I like it more than I expected.
“그 재킷 하나 걸치니까 딱 꾸안꾸 느낌이야.”
That jacket gives the outfit just the right effortlessly styled feel.
Sources
National Institute of Korean Language
References support the meaning and usage. Example sentences are written for NoCapWiki.