solar plexus
US /ˈsoʊ.lər ˈplek.səs/
UK /ˈsoʊ.lər ˈplek.səs/

1.
a complex of nerves and ganglia situated in the pit of the stomach, behind the stomach, and in front of the aorta, often associated with a feeling of vulnerability or a blow to the stomach
:
•
He took a hard punch to the solar plexus and gasped for air.
•
A sudden fright can make you feel a knot in your solar plexus.