first-come-first-serve
Adjective Satellite
Meaning
not accepting reservations
Source: WordNetSynonyms
Examples
This is first-come-first-serve, and no, we DO NOT have any other codes.
Pre-orders for the PS5 are currently available via an invite system, though reservations are on a first-come-first-serve basis.
The selection will be on a first-come-first-serve basis.