adjective
1.
[ usually before noun ] in the best group; of the highest standard
SYN excellent :
a first-class novel
a first-class writer
The car was in first-class condition.
I know a place where the food is first-class.
2.
[ only before noun ] connected with the best and most expensive way of travelling on a train, plane or ship :
first-class rail travel
a first-class cabin / seat / ticket
3.
[ only before noun ] (in Britain) connected with letters, packages, etc. that are delivered most quickly, or that cost more to send :
first-class mail / post / postage / stamps
4.
[ only before noun ] used to describe a university degree of the highest class from a British university :
She was awarded a first-class degree in English.