firstclass
adjectiveUK /ˌfɜːst ˈklɑːs/
US /ˌfɜːrst ˈklæs/
The very best kind of something.
She gave a firstclass performance in the school play.
OTHER MEANINGS
2. The best and most expensive seats or rooms on a train, plane, or ship.
They traveled firstclass on the train to the coast.
3. A mark of the highest grade on a test or in school.
He earned a firstclass degree in science.
4. Mail that is handled fastest and costs the most to send.
Send the letter by firstclass mail so it arrives tomorrow.