The antonyms for the phrase "curved inward" could include "curved outward," "straight," "flat," or "convex." When something is described as "curved inward," it typically means that the surface or shape is concave or indented. For example, a bowl, a spoon, or a crescent moon all have a curved inward shape. On the other hand, objects with an opposite shape are described as "curved outward," such as a bubble, a dome, or a sphere. If something is "straight," it has a linear shape without any curves, while "flat" refers to a surface that is level, smooth, and even. Finally, "convex" is used to describe a surface that bulges or protrudes outward.