fourth class

US: (fôrth′klas′, -kläs′, fōrth′-)

WordReference Random House Learner's Dictionary of American English © 2026

ˈfourth ˈclass, n. [uncountable]

1. Stamps a class of mail consisting of merchandise weighing one pound or more and not sealed against inspection.

fourth--class, adj., adv. 

WordReference Random House Unabridged Dictionary of American English © 2026

fourth′ class′, 

1. Stamps (in the U.S. Postal Service) the class of mail consisting of merchandise weighing one pound or more, including parcel post and all first-, second-, or third-class matter weighing 8 oz. (227 g) or more and not sealed against inspection.

• 1860–65, American.

fourth-class  (fôrth′klas′, -kläs′, fōrth′-), adj. 

1. of, pertaining to, or designated as a class next below third, as for mailing, shipping, etc.

adv. 

2. Stamps as fourth-class matter;
   by fourth-class mail:
   Send it fourth-class.