first class

UK: /ˌfɜː^rstˈklɑːs/ US: (fûrst′klas′, -kläs′)

WordReference Random House Learner's Dictionary of American English © 2025

ˈfirst ˈclass, n. [uncountable]

1. the best, finest, or highest class, grade, or rank.
2. Stamps a class of mail consisting of materials, as letters, sealed against inspection.

first--class, adj., adv. 

WordReference Random House Unabridged Dictionary of American English © 2025

first′ class′, 

1. the best, finest, or highest class, grade, or rank.
2. the most expensive and most luxurious class of accommodation on trains, ships, airplanes, etc.
3. Stamps (in the U.S. Postal Service) the class of mail consisting of letters, postal cards, or the like, together with all mailable matter sealed against inspection.
4. [Brit. Univ.] the group receiving the highest distinction in an honors course.
• 1740–50

first-class  (fûrst′klas′, -kläs′), adj. 

1. of the highest or best class or quality:
   a first-class movie.
2. best-equipped and most expensive:
   a first-class railroad car.
3. Stamps given or entitled to preferred treatment, handling, etc.:
   first-class mail.

adv. 

4. by first-class conveyance:
   to travel first-class.

• 1780–90

Collins Concise English Dictionary © HarperCollins Publishers::

first class noun

1. the class or grade of the best or highest value, quality, etc

adjective (first-class when prenominal)

1. of the best or highest class or grade: a first-class citizen
2. excellent; first-rate
3. of or denoting the most comfortable and expensive class of accommodation in a hotel, aircraft, train, etc
4. (in Britain) of or relating to mail that is processed most quickly
5. (in the US and Canada) of or relating to mail that consists mainly of written letters, cards, etc
6. See first10

adverb first-class

1. by first-class mail, means of transportation, etc