[fourth class] n (1862) 1: a class or group ranking fourth in a series
2: a class of mail in the U.S. that comprises merchandise and non-second-class printed matter and is not sealed against inspection
[fourth class] n (1862) 1: a class or group ranking fourth in a series
2: a class of mail in the U.S. that comprises merchandise and non-second-class printed matter and is not sealed against inspection
Merriam-Webster English vocab. Английский словарь Merriam Webster. 2012