1. What does it mean?
플러팅 borrows English 'flirting.' It describes behavior intended, or interpreted, as showing romantic interest without necessarily making a direct confession or establishing a relationship.
Also written or said as peulleoting
2. The nuance
Friendly behavior is not automatically flirting, and perceived flirting is not consent to anything further. The same compliment can have different meanings depending on the people and situation.
3. Examples
“칭찬이 플러팅인지 그냥 친절한 건지 아직 모르겠어.”
I don't know yet whether the compliment was flirting or just friendliness.
“상대가 불편해 보여서 플러팅을 멈추고 거리를 뒀어.”
They seemed uncomfortable, so I stopped flirting and gave them space.
Sources
References support the meaning and usage. Example sentences are written for NoCapWiki.