what is reservation
noun. The definition of a reservation is something withheld or the act of withholding something. 1  An example of reservation is someone calling a restaurant and asking them to hold a table for a specific time. 2  An example of reservation is a concern that holds a person back from doing something.he definition of a reservation is something withheld or the act of withholding something. 1  An example of reservation is someone calling a restaurant and asking them to hold a table for a specific time.