1. To rush, to pour, or to surge back; to flow or to allow to flow backward.
2. To bring gastric or esophageal contents back up into the mouth (vomit, throw up, puke) or to eject the contents of the stomach through the mouth.
3. To cause to surge back, as partially digested food; to vomit.
4. A reference to some creatures that bring food that has been swallowed back to and out of the mouth: Some birds regurgitate food to feed their young.

See reflux for a related word.