Depressed; concave; gaunt; sunken.

A low spot surrounded by elevations; a depressed part of a surface; a concavity; a channel.

a depression hollowed out of solid matter

The groove down the middle of the bottom of a figure skate blade is called the hollow. Finely ground edges on either side of the hollow provide control and speed. The depth of the hollow varies depending on the skater's event, weight and style.

The depression between the Tower Ridge and the Next Ridge.

The concave space between the two edges of a skate blade that runs the length of the blade.