a cavity or space in something
- "hunger had caused the hollows in their cheeks"
a small valley between mountains
- "he built himself a cabin in a hollow high up in the Appalachians"
not solid; having a space or gap or cavity
- "his face became gaunter and more hollow with each year"
- "hollow cheeks"
- "a hollow tree"
- "a hollow wall"
as if echoing in a hollow space
- "the hollow sound of footsteps in the empty ballroom"