What is another word for "concavity"?

Roget's Thesaurus (1911) lists these synonyms for "concavity": abase, abasement, abdomen, abdominal, about, abysmal, and, ankle, backbone, bathometer, bathymetry, belly, bend, benthal, beyond, bob, bosom, bottomless, bow, breast, bring, cast, cave, center, circumscribe, coeliac, contents, couch, courtesy, cower, crater, crouch, curtsy, cut, dash, debase, deep, deepen, deepness, depress.