"Hollow space" refers to a void or empty area inside an object or between objects, with nothing filling that area. It describes a space that has no solid matter or substance. Full definition
Dig beneath the surface of many law firm brands, and you'll strike hollow space a lot sooner than you might think. (slaw.ca)
Some can barely wend their way through their kitchen for all the foil - covered dishes borne over by neighbors doing what they can to fill the suddenly hollow space in a once - full home. (religion.blogs.cnn.com)
The key to the liver's ability to eliminate excess bile is the fact that the «tubes» through which bile enters the biliary tract are not merely a set of inactive pipes, but are actually hollow spaces between living cells. (sciencedaily.com)