What is the medical definition of eructation?

An eructation is the medical term for a burp (belch). Belching is a protective mechanism that prevents the stomach from overinflating. Every time you swallow, you take in a little air, and some of it travels down the esophagus and gets into the upper part of the stomach. When the stomach begins to stretch out, sensors in its wall send signals to your esophagus. These signals tell the small ring of muscle (sphincter) at the bottom of the esophagus to open a bit, allowing air that has built up in the stomach to escape.