According to MediLexion, prepyloric describes something anterior to or preceding the pylorus. It also denotes a temporary constriction of the wall of the stomach separating the fundus from the antrum during digestion.
According to Wikipedia, the pylorus is the region of the stomach that connects to the duodenum. The pylorus is part of the gastrointestinal system. The pylorus functions as a regulator for food that passes from the stomach to the duodenum. This regulation is done by a part of the pylorus called the pyloric sphincter.
According to the US National Library of Medicine, prepyloric is used to denote the location of problems in the stomach area, commonly ulcers. An example of its usage can be found in a short article published in the National Library of Medicine, which compares and contrasts the difficulties of treating prepyloric ulcers and duodenal ulcers. According to this article, they are similar in almost every way except for location.
According to HealthTap, another common use of the term is prepyloric stomach inflammation. Again, this usage of the word is to indicate location, often being compared and opposed to the duodenum.
According to MediLexicon, there is also a prepyloric vein, which is a tributary of the right gastric vein that passes anterior to the pylorus, where it connects with the duodenum.