When you invert something, you turn it upside down, whether it’s an idea or a test you place face-down on your desk when you are finished.
Invert comes from the Latin word invertere, which means "to turn." For example, you might invert a cake pan, turning it upside down on a plate in order to remove the cake. Or if you have a long-standing belief, say, that cats make bad pets, spending time with a really great cat may make you turn that belief upside down, inverting it. And you might even get a cat of your own!