I. kän-ˈkāv, ˈkän-ˌ adjective
Etymology: Middle English, from Latin concavus, from com- + cavus hollow — more at cave
Date: 15th century
1. : hollowed or rounded inward like the inside of a bowl
2. : arched in : curving in — used of the side of a curve or surface on which neighboring normals to the curve or surface converge and on which lies the chord joining two neighboring points of the curve or surface
II. ˈkän-ˌkāv noun
Date: 1552
: a concave line or surface