noun. a flow that returns toward its source.
1. Adjective Switch the filter pump on your hot tub into the “Off” position before beginning backflow operations. 2. Preposition or subordinating conjunction The exhaust system is cast iron with a dry-joint elbow to prevent water backflow through the engine. 3. Noun, singular or mass Follow this with the heparin, and as you inject the last of the heparin, close the clamp on the tubing to stop any backflow of blood. 4. Verb, base form Water can backflow into the washing machine if the drain hose is lifted too high. 5. Verb, non-3rd person singular present Gastroesophageal reflux disease occurs when stomach acids backflow into the esophagus.