1. A cavity or space in something.
2. A small valley between mountains; SYN. holler.

ETYM Old Eng. holow, holgh, holf, AS. holh a hollow, hole. Related to Hole.
1. As if echoing in a hollow space.
2. Not solid; having a space or gap or cavity.

To remove the interior of; SYN. hollow out, core out.

1. Ao as to have a hollow sound
2. Completely, thoroughly