(US) A former class of mail consisting mostly of heavier printed matter.

A social and economic demographic, commonly identified as part of the upper middle class. / (in the plural) The groups in society composed of highly educated professionals.

Alternative spelling of working-class

The social class of those who perform physical work for a living, as opposed to the professional or middle class, the upper class, or others.

(set theory) Any one of the subsets into which an equivalence relation partitions a set, each of these subsets containing all the elements of the set that are equivalent under the equivalence relation.

occupying a position between the upper class and the working class

A social and economic class lying above the working class and below the upper class.

(law, chiefly US, Canada) A lawsuit brought by a single plaintiff or small group of plaintiffs as a representative of a large group of others having a common interest, with everyone in the large group eligible to receive damages if the plaintiff is successful.

of high social position / aristocratic

those people at the top of a social hierarchy / the aristocracy