Water-brashes or acid reflux are caused by stomach acid flowing back up into the esophagus. There are several synonyms for water-brashes, including heartburn, pyrosis, acid indigestion, and gastroesophageal reflux disease (GERD). Heartburn is a common term used to describe the burning feeling in the chest and throat that results from acid reflux. Pyrosis is another term that signifies a burning sensation in the upper abdomen or chest. Acid indigestion refers to the discomfort felt when stomach acid rises up to the esophagus causing painful symptoms. GERD refers to a more severe condition of frequent and persistent acid reflux, which can lead to complications like esophagitis or Barrett's esophagus.