fourth class

fourth class (uncountable)

1. A (former) class of mail in the United States and Canada.
2. (rail transport) A class of rail travel formerly found in some countries.
   • 1946 May and June, “Notes and News: Russian Coach Colours”, in Railway Magazine, pages 184–185:

     […] Mr. S. C. Hawtrey writes that when he knew the Moscow-Kazan Railway (then under British management) in 1913, it was a regular practice in Russia to paint the exterior of first class coaches blue, second class yellow, third class green, and fourth class, where it still survived, brown.

• “fourth class”, in Merriam-Webster Online Dictionary, Springfield, Mass.: Merriam-Webster, 1996–present.