1. The first, highest, or best group in a system of classification: a restaurant of the first class.
2. The most luxurious and most expensive class of accommodations on a train, passenger ship, airplane, or other conveyance.
3. A class of mail including letters, post cards, and sealed packages.

The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.