1.Definition: as if echoing in a hollow space

"The hollow sound of footsteps in the empty ballroom"

2.Definition: devoid of significance or force

"A hollow victory"

Related Adjective(s):empty, vacuous

3.Definition: lacking in substance or character

"A hollow person"

4.Definition: not solid; having a space or gap or cavity

"A hollow wall", "A hollow tree", "Hollow cheeks", "His face became gaunter and more hollow with each year"