Hollow/ˈhɑːləʊ/ Definition 1 of 4Pro Tip 1/2Physical emptiness Use 'hollow' to describe objects that are empty on the inside, like tubes or boxes. She tapped the wall, looking for the hollow parts. Pro Tip 2/2Sound quality 'Hollow' can also describe a sound that echoes, as if coming from an empty space. The room's acoustics made her voice sound hollow.