Definition of reflux in US English:



mass noun
  • 1Medicine
    The flow of a fluid through a vessel or valve in the body in a direction opposite to normal.

    ‘the majority of leg ulcer patients are elderly with simple superficial vein reflux’
    ‘the main culprit is bile reflux, a backup of digestive fluid that is supposed to remain in the small intestine’
    1. 1.1 A condition in which acidic gastric fluid overflows into the esophagus, resulting in heartburn.
      ‘knowing which foods cause reflux is crucial in alleviating symptoms’
      as modifier ‘patients with reflux esophagitis’
      • ‘Just doors away on the same street, Paul Samuels suffered numerous urinary infections and was also diagnosed with the same reflux as the Buckley and Chapman children.’
      • ‘He was also experiencing increased heartburn and obvious gastroesophageal reflux.’
      • ‘I also had a child with reflux [a kidney infection], which meant she couldn't sleep lying down.’
      • ‘Most investigators consider any esophageal pH below 4.0 as the cutoff defining reflux of gastric acid into the esophagus.’
      • ‘I would not have diagnosed reflux on the basis of those records.’
    2. 1.2 (in a baby after feeding) the regurgitation of the contents of the stomach into the mouth.
      ‘babies are prone to reflux because they have tiny stomachs’
  • 2Chemistry
    The process of boiling a liquid so that any vapor is liquefied and returned to the stock.

    ‘the mixture was heated at reflux under nitrogen’
    • ‘After separation by TLC and elution from the silica gel, ASG and SG were hydrolysed with 2 N methanolic HCl under reflux for 4 h at 100°C.’
    • ‘For water extraction of Sophora flavescens, 200 g of dried root was mixed with 1,800 ml of distilled water and extracted under reflux for 3 hr by boiling the mixture.’
    • ‘Sugar concentrations in the tips were measured after extraction two times in 4 ml of 80% ethanol boiled with reflux for 20 min.’
    • ‘In general, distillation can be carried out either with or without reflux.’
    • ‘They looked at various substituted benzaldehydes and cyanoamides and compared the results of traditional ethanol reflux, water reflux and solvent-free conditions.’


  • 1Medicine
    no object, with adverbial of direction (of a fluid) flow backwards through a vessel or valve in the body.

    ‘acidic secretions of the stomach can reflux back upwards’
    • ‘If the muscular valve above the stomach leaks, food mixed with acid washes back, or refluxes, into the esophagus.’
    • ‘Normally, this muscle is always contracted, preventing acid from refluxing into the esophagus.’
    • ‘The main function of pyloric closure is to reduce the volume of fluid that refluxes into the distal stomach from the duodenum.’
    • ‘Gastro-oesophageal reflux disease is defined as symptoms or mucosal damage resulting from the exposure of the distal oesophagus to refluxed gastric contents.’
    • ‘The reflex peristaltic contraction sweeps any refluxed gastric fluid back into the stomach.’
  • 2Chemistry
    Boil or cause to boil in circumstances such that the vapor returns to the stock of liquid after condensing.

    no object ‘the liquid is allowed to reflux until the thermometer records the lowest temperature possible’
    with object ‘the solutions were refluxed for 9–12 hours’
    • ‘Until 1991, the Defendants manufactured on the site prochloraz-manganese complex; the process involved refluxing prochloraz with manganese chloride, an inorganic compound.’
    • ‘Three liters of 95% ethanol were added to each bottle and then refluxed for 4 hours.’
    • ‘Ginseng root was refluxed with ethanol, and WSF and LSF were prepared from this ethanol extract.’
    • ‘Second, the alkaloid is refluxed with acetic anhydride for about five hours.’
    • ‘In the laboratory higher concentration ethanol, with less water, can be produced by refluxing the rectified spirit with quicklime and then distilling the alcohol mixture.’


Middle English: from re- and flux.