stray sheep; lost lamb; person at a loss
Literally a stray sheep or lost lamb; figuratively, a person who is lost, confused, or doesn't know what to do. Often carries a sympathetic or slightly poetic tone.
Since quitting his job, he's like a lost lamb.
All new students are like stray sheep.
A set phrase combining the classical attributive form 迷える (mayoeru, 'straying/lost') of the verb 迷う (mayou) with 子羊 (kohitsuji, 'lamb'). The figurative use is influenced by the Christian parable of the Lost Sheep.