Jejunum

n. middle part of the small intestine (Anatomy)

In anatomy of the digestive system, the jejunum is the central of the three divisions of the small intestine and lies between the duodenum and the ileum. The change from the duodenum to the jejunum is usually defined as the ligament of Treitz. In adult humans, the small intestine is usually between 5.5-6m long, 2.5m of which is the jejunum. The pH in the jejunum is usually between 7 and 8 (neutral or slightly alkaline).
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n. jejunum, middle part of the small intestine (Anatomy)

(n.)
The middle division of the small intestine, between the duodenum and ileum; -- so called because usually found empty after death.
  

Part of the small intestine. It is half-way down the small intestine between its duodenum and ileum sections.