having a recessed surface; curved inwards; concave; sunken

hollow cheeks

having a cavity within

a hollow tree

echoing like a sound made in or by beating on an empty container; muffled

speaking in a hollow voice

(usu + out) to make hollow or form by hollowing

(usu + out) to make a cavity in (something)

canoes made from hollowed-out tree trunks

(usu + out) to make (a cavity) in something

They hollowed out a shelter in the snow

a depressed or hollow part of a surface; esp a small valley or basin

a wooded hollow

an unfilled space; a cavity

in the hollow of one's hand