Definition of "concave" [con•cave]

• Curved like the inner surface of a sphere. (adjective)
• A concave surface, structure, or line. (noun)
• To make concave. (verb-transitive)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "It flowed in a gentle concave from the road up the mountain, its farther boundary an unbroken line of timber."
• "The last three types, called concave lenses, scatter parallel rays so that they do not come to a focus, but diverge widely after passage through the lens."
• "That surface of the bow which faces the string when drawn into action, that is, the concave arc, is called the belly of the bow."