Hmph is a snorting sound people make through their nose to show disapproval, skepticism, or dismissal. It's not really a word you say out loud with your mouth: it's more like a sharp exhale through your nostrils while keeping your lips closed.

When your older brother claims he can beat the video game level in one try and you doubt it, you might respond with “Hmph!” instead of arguing. When a character in a book feels insulted or thinks someone else is being foolish, the author might write that they said “Hmph” and walked away with their nose in the air.

The sound carries attitude. It's a way of expressing I don't believe you, or That's ridiculous, or I'm not impressed without using actual words. Sometimes people use it playfully, and sometimes they mean it seriously. You can often tell the difference by whether the person is smiling or frowning when they make the sound.

Hmph appears most often in written dialogue to capture this distinctive sound. In real conversation, people make this noise all the time, but they rarely think of it as a “word” until they see it written down in a story.