IPA: /ˈpriːbʊkt/
KK: /priˈbʊkt/
Arranged or reserved ahead of time, usually for travel or accommodation.
We have a prebooked hotel room waiting for us when we arrive.
Prebooked → It is formed from "pre-" (meaning before) and "booked" (from the verb "book", which comes from Old English "bocian", meaning to reserve or arrange). The word "prebooked" means arranged or reserved in advance.
Think of making a reservation "before" ("pre-") the actual event — that's why prebooked means to have something reserved ahead of time.