The condition where stomach acid unwantedly and uncontrollably makes it up your esophagus, and sometimes is regurgutated. It is an almost puke, but containing only acid. Often happens when you haven't eaten anything for a long time and acid builds up in your stomach, but it can be a chronic thing as well. Often associated with heartburn.

There are surgical operations available to control acid reflux which involve recontouring your esophagus, but the downside is that they make it impossible to burp or throw up when you really need to.