Vroomp

Similar to a burp, however it's more like an airbubble that does not reach "burp" status. The air bubble stops at the throat and makes a noise that sounds like "vrrrooommppp" on the way up. It does not escape from your mouth (because it stops around your throat.)

An air bubble travelling up your pipes that makes a noise like vroooomp and your hoping the person next to you can't hear it. Except they always can. "I just vroomped"