But among the tasks the machine can perform in a single step are edge detection, inversion, the identification of lines and shapes of different orientations, and the filling-in of concave shapes all things that are useful in image-processing, and not all of which can be managed by digital technology.

ECONOMIST: Analogue computing

The indoor portion of the observation deck includes a pair of over-size, concave mirrors that produce fun-house reflections of visitors.

BBC: Orbiting views of Olympic London

Her waist was concave at the small of her back.

NEWYORKER: The House Behind a Weeping Cherry

The result, in his final sketch of the Z4, was a roadster with edgier lines than its predecessor and intertwining concave and convex surfaces, echoing the geometry of a Cubist painting.

WSJ: Anders Warming: The Man Who Reinvents Wheels | Creating

My chest was concave when I was a child, but if you look closely, this is true of most children, and the weight lifting I did in prison helped with that, and while I don't actually have a barrel chest, I might have a half barrel.

NPR: Chapter 1