sound somebody out about something

Từ điển Oxford Advanced Learner 8th

ˌsound sbˈout (about/on sth) | ˌsound sthˈout derived
to try to find out from sb what they think about sth, often in an indirect way
•I wanted to sound him out about a job.
•They decided to sound out her interest in the project.
Main entry: ↑sound_derived