What is pre-authorization?

Answer 1

To have got permission to do something before you actually need it. It is often used in a security context. Someone going to a restricted area has already been given permission to go there, so does not seek it on arrival. They may have something like a code that gives them access. It can be used in other contexts, such as in a credit card situation, where someone has been given permission to use it or to use it for beyond its normal limits.