Retching is a process in the human body where gastric (and sometimes duodenal) contents are forced into the esophagus, but do not enter the pharynx. Retching usually precedes vomiting, when the upper esophageal sphincter remains closed. If the upper esophageal sphincter is open, vomiting occurs. ^[1].

References

1. ^ Berne, Robert M.; Matthew N. Levy (2004). Physiology. Elsevier Mosby, p. 557. ISBN 0-323-03390-3.