intransitive. To form a hollow or hollows resembling a valley.

To bend or curve downwards in the middle, from its own weight or superincumbent pressure. Said, e.g., of a rope supported at two points, of a beam…

intransitive. To form a cup; to be or become cup-shaped.

intransitive. To become hollow or concave.

intransitive. To have the shape of a saucer; to dip in the centre; to be concave. rare.