I've heard calling tapes describe the word as "Hut" or "Fut", but in reality is is NO word that we speak.
Since the tongue rides up and touches the top of the mouth, just behind the front teeth, it's more like the air you push out while trying to make a single whistle between puckered lips.
Air is pushed out, then cut off by your diaphram, filling your mouth cavity, and as the pressure starts to drop, your tongue follows the last of it and kind of helps keep the pressure there, but still lets it's fall a little.
To me the "word" would be somethinng like "Fwhit". There is no SPOKEN word (at least I don't), but that's what I'd be saying, the way I shape my mouth, IF I actually said a word.