concave shape
concavity
incurvation
incurvature

The painstaking process begins by hammering the base of an oil drum into a concave shape.

The gorget forms a concave shape and, when engraved, the interior is polished and decorated.

This concave shape will help disperse sound and increase intelligibility.

The retroflex sounds, however, have a flat or concave shape, with no associated palatalization, and no groove running down the tongue.

At one end is a black granite fountain with a double concave shape.

Oreum is a parasitic volcano, and its top has a concave shape.

The male can be identified by the slightly concave shape to its plastron.

Out-cannel gouges are used to cut concave shapes, like finger-pull slots, out of wood.

Its panels are curved, so the visitor pushes into a concave shape - a particularly elegant experience.

In addition, the females plastron is much flatter than that of the males which has a concave shape.