What do you mean by...?

John: I didn't quite catch that. What do you mean by 'ubiquitous'?

Alice: It means something that is present, appearing, or found everywhere. What do you mean by using that word in this context?

John: Oh, I just meant it's very common. What do you mean by 'ubiquitous' being used?

Alice: It's used to imply a widespread prevalence.