경비실이 · 경비실을
security office, guard booth (in an apartment complex)
Example
택배는 경비실에 맡겨 주세요.
Please leave the package at the security office.
Word parts
경 guard+비 prepare+실 room
Literally 'guard room'. -실 = room: 경비실, 화장실, 사무실.
Good to know
In Korean apartment complexes, the 경비실 often holds parcels for residents who are out.