1. first come first served - Noun
2. first come first served - Adjective
first come first served (uncountable)
(operations) A service policy in which the first to arrive for service receives the service first.
first-come-first-served (not comparable)
Describing a process of dealing with people using the principle "first come, first served".
first-come-first-served
The FCC put a freeze on those licenses because the agency was considering auctioning them off to the highest bidder rather than granting them on a first-come-first-served basis. Source: Internet
When tickets are sold on a first-come-first-served basis, those tiny advantages can automatically push fans to the end of the line. Source: Internet