Nuance Dictionary / Social Awkwardness
뻘쭘하다 ppeol-jjum-ha-da
Feeling incredibly awkward, out of place, and foolish in a social situation
Imagine waving enthusiastically at someone across the street, only to realize they were waving at the person behind you. Your hand freezes in the air. At that moment, you are absolutely '뻘쭘하다'.