1) Abdomen part 2) Abdominal network 3) Bad place for a blow 
The ganglion of nerve cells and fibers situated at the back of the abdomen which subserves autonomic nervous system function for much of the gastrointestinal tract. A sharp blow on the abdomen over the solar plexus causes visceral pain and 'winding.'
coeliac (nervous) plexus ... 
celiac plexus (def. 1).
Type: Term Synonyms: celiac (nerve) plexus
The solar plexus is a network of nerves situated in the abdomen behind the stomach. It surrounds the coeliac axis, the thick short artery which is a branch of the aorta. The solar plexus contains several ganglia or collections of nerve cells, and from it nerve filaments go to all the abdominal viscera. A blow to the pit of the stomach is the so-cal...
[n] - a large plexus of sympathetic nerves in the abdomen behind the stomach
the largest network of nerves in the body, located behind the stomach 
coeliac plexus noun a large plexus of sympathetic nerves in the abdomen behind the stomach
the pit of the stomach.
a large plexus of sympathetic nerves in the abdomen behind the stomach