The floor was slightly concave with a drain in its center.

They were slightly concave, and each had some complicated mechanism at its focus.

The walls curved into the overhead, which itself was slightly concave.

The transition between the shoulder and the sutures is slightly concave.

This information then appeared on the world map which took up the entire wall, slightly concave, opposite the gallery.

But she saw that the rock face was slightly concave.

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

They were hidden from the town by the slightly concave curve of the cliffs.

But it was definitely a reflection, slightly concave and probably coming from a watch crystal.

Certainly not its standard English meaning, "a slightly concave plate on which to serve food."