acid reflux

noun

: backward flow of the acidic contents of the stomach into the esophagus that is due to malfunctioning of a sphincter at the lower end of the esophagus and that results especially in heartburn : gastroesophageal reflux

a medication for acid reflux

Acid reflux is the backflow of stomach contents into the esophagus. The feeling of acid reflux is heartburn: a mild burning sensation in the mid-chest …

—The Tennessee Tribune

Acid reflux occurs when the valve between your esophagus and stomach doesn't close properly, allowing stomach acid to wash back up through your esophagus …

—Miriam Jones Bradley

Examples of acid reflux in a Sentence

Recent Examples on the Web

Compounding the issue is that many symptoms of gastrointestinal cancers, such as stomach pain, bloating, indigestion, and acid reflux, can mimic more common gut issues like irritable bowel syndrome, inflammatory bowel disease, or Crohn’s disease. —Brian Mastroianni, Health, 19 Aug. 2025

While acid reflux happens occasionally, GERD is a chronic condition where acid reflux occurs more than twice a week when stomach acid travels back up into the esophagus, causing heartburn. —Elizabeth Yuko, Flow Space, 21 July 2025

Among medical causes of halitosis, acid reflux is one of the more manageable. —Betsy Andrews, Saveur, 17 July 2025

This backwash, also known as acid reflux, irritates the lining of your esophagus. —Elizabeth Ayoola, Essence, 3 July 2025

Word History

First Known Use

1960, in the meaning defined above

Medical Definition

acid reflux

noun

: backward flow of the acidic contents of the stomach into the esophagus that is due to malfunctioning of a sphincter at the lower end of the esophagus and that results especially in heartburn : gastroesophageal reflux

… people who report experiencing at least weekly symptoms of acid reflux have substantially higher risks of BE [=Barrett's esophagus] than those with less frequent episodes. Moreover, we found that symptoms of acid reflux experienced at older ages conferred substantially higher risks of BE than symptoms at younger ages …

—Kylie J. Smith et al., Cancer Epidemiology, Biomarkers & Prevention