What is huh? in German? Huh? French? Huh? English? Huh? Spanish? Huh? And, in at least six other languages, including Chinese. I learned that in an article by Arika Okrent in the Smithsonian magazine.
I looked it up in Merriam-Webster and, indeed, it is a word, an interjection meaning a whole bunch of things. It’s all in the way you say it. Depending on your intonation, it can mean that you’re asking if someone agrees with you, and that you misunderstood or didn’t hear what another person says, or you can use it to show surprise, disbelief, or disapproval.
You can thank Mark Dingemanse and the Max Planck Institute for Psycholinguistics, in Nijmegan, the Netherlands for bringing that to the world’s attention. Huh? is the first “universal word” studied by modern linguist.
Remember, you read it here.