What does sonder mean?

@C0102
It means « to poll », « to survey » or « to sound out ».

When you « sonder » someone for a poll, you’re making a « sondage » (survey). You’re gathering opinions about a same topic.

People asked for the survey are often called « sondés ». This is something you often hear on tv :
« …% des sondés pensent que… »

But you can also use it when you’re trying to understand someone. You use « sonder » like you were a scanner, analyzing everything you can see with this person. We sometimes use it but it’s not very common with this meaning.