pl. of Viscus., of Viscus

The plural for the noun viscus is viscera.

mistletoe

Viscus means organ. So hollow viscus means an organ than has a lumen or open space within it, like the stomach and intestines. Perforated hollow viscus is an organ with a lumen that has a hole in it such that contents can escape from inside the organ to outside the organ. If a gastric ulcer perforated, it would be a perforated hollow viscus, allowing gastric acid and contents out into the abdominal cavity.

Visera is the plural of viscus, which are your internal organs.