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

Other factors can also interfere with absorption, including gastrointestinal conditions that affect nutrient uptake and certain medications, such as proton pump inhibitors (PPIs) used to treat acid reflux. — Morgan Pearson, Verywell Health, 7 July 2026

Diet changes are among the most common tweaks people with acid reflux make. — Sarah Klein, Time, 30 June 2026

For instance, people prone to acid reflux or migraines sometimes find that chocolate can trigger symptoms. — Daryl Austin, USA Today, 27 June 2026

The second letter of the condition known as GERD refers to what body part, into which stomach acid refluxes during flare-ups of the disease? — Drew Goins, The Atlantic, 26 June 2026

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