concav

a. [ L. concavus; con- + cavus hollow: cf. F. concave. See Cave a hollow. ] 1. Hollow and curved or rounded; vaulted; -- said of the interior of a curved surface or line, as of the curve of the of the inner surface of an eggshell, in opposition to convex; as, a concave mirror; the concave arch of the sky. [ 1913 Webster ]

2. Hollow; void of contents. [ R. ] [ 1913 Webster ]

As concave . . . as a worm-eaten nut. Shak. [ 1913 Webster ]

v. t. [ imp. & p. p. concaved p. pr. & vb. n. Concaving. ] To make hollow or concave. [ 1913 Webster ]

n. [ L. concavum. ] 1. A hollow; an arched vault; a cavity; a recess. [ 1913 Webster ]

Up to the fiery concave towering hight. Milton. [ 1913 Webster ]

2. (Mech.) A curved sheath or breasting for a revolving cylinder or roll. [ 1913 Webster ]

a. (Her.) Bowed in the form of an arch; -- called also arched. [ 1913 Webster ]

n. Hollowness; concavity. [ 1913 Webster ]

n.; pl. Concavities [ L. concavitas: cf. F. concavité. See Concave. ] A concave surface, or the space bounded by it; the state of being concave. [ 1913 Webster ]

a. Concave or hollow on both sides; double concave. [ 1913 Webster ]

a. 1. Concave on one side and convex on the other, as an eggshell or a crescent. [ 1913 Webster ]

2. (Optics) Specifically, having such a combination of concave and convex sides as makes the focal axis the shortest line between them. See Illust. under Lens. [ 1913 Webster ]