홀연 사라지다 · 홀연히 (same meaning)
suddenly, all of a sudden, unexpectedly
Example
그는 어느 날 홀연 자취를 감췄어요.
One day he suddenly vanished without a trace.
Word parts
홀 sudden+연 -ly, so
Literally 'in a sudden manner'; a literary word from stories and essays.
Good to know
Literary; in everyday speech say 갑자기 instead.
Related words