1. What does it mean?
공시생 abbreviates 공무원 시험 준비생. It refers to a person studying for an exam used in civil-service recruitment, rather than every job seeker or every person preparing for a test.
Also written or said as gongsisaeng
2. The nuance
The label does not specify their age, exact exam, or number of attempts. It describes preparation, not an already secured government job.
3. Examples
“공시생 친구는 오전마다 공부 계획을 세워.”
My friend who is preparing for the civil-service exam plans their study each morning.
“공시생이라고 하루 일정이 모두 같은 건 아니야.”
Not every civil-service exam candidate follows the same daily schedule.
Sources
References support the meaning and usage. Example sentences are written for NoCapWiki.