아싸 /a-ssa/
Outsider / Loner
Short for 'outsider' — someone who prefers being alone or doesn't fit into mainstream social circles. Often used self-deprecatingly or affectionately.
Examples
나 완전 아싸라서 파티 별로야
I'm such an outsider, parties aren't really my thing
아싸 라이프도 나쁘지 않아
The loner life isn't so bad