A lost child or person; someone (often a child) who has become separated from their guardian or gotten lost.
駅で迷子のお知らせが流れた。
An announcement about a lost child was played at the station.
公園で迷子になって泣いている子を見つけた。
I found a child crying in the park who had gotten lost.
親は迷子防止のために連絡先を書いた名札を持たせた。
The parents had the child wear a name tag with contact information to prevent them getting lost.