1. if something is first-class, it is of very good quality and much better than other things of the same type:
• We provide a first-class, professional service for our customers.
2. using first-class mail:
• a first-class stamp
3. TRAVEL first class seats, accommodation etc are the most comfortable and expensive available:
• first-class airline tickets
• The airline claims its 9,000 daily first-class seats are 65% full.
— first class adverb :
• If you send the letter first class, it should arrive tomorrow.
• Company policy says we cannot fly first class, but we can fly business class on trips over a thousand miles.
Financial and business terms. 2012.