Casual Conversation with him

Had the following conversation with a guy I went to high school with:

Him: "Hey, what does 'redundant' mean?"
Me: "It means saying the same thing twice, like adding unnecessary detail. Like if you said 'wet water'."

Him: "So it means stupid?"
Me: "No, it doesn't mean 'stupid' it means saying the same thing twice basically"
Him: "So if I said dog dog? Like said the word dog twice."
Me: "No, not really-" Him "-but if I did that it would be stupid, right? So it means stupid."

This went on for longer than I'm proud of, and that guy, as far as I know, still thinks redundant means 'stupid'. I heard him use it that way multiple times before we graduated.

I'm willing to concede that my 10th grade definition of "redundant" wasn't exactly on-the-nose, but it still doesn't mean stupid