This is the 1673rd most frequent Korean word.
신고했다
"Reported" or "filed a report."
Here, '신고했다' means 'reported' and is used in the context of notifying authorities about an incident.
나는 경찰에 사건을 신고했다.
I reported the incident to the police.
In this sentence, '신고했다' indicates the action of reporting a discovery of a crime to relevant authorities.
그는 도둑을 발견하고 신고했다.
He discovered the thief and reported it.
This usage of '신고했다' refers to reporting a specific violation, in this case, illegal parking.