A category or class of mail which is prioritized in some way; now esp. (in the United States) the class of mail that is used for lighter items…

The second of a ranked series of classes in which things are grouped; esp. of university degrees, railway carriages, and mail.

U.S. A local post office; an item of mail addressed to a local post office. Obsolete.

attributive or adj. Of or belonging to the class next below the second.

colloquial. An item of registered mail.

Unwanted or unsolicited mail or post, typically in the form of circulars, advertisements, etc., sent to a large number of addresses.

advertising matter or the like sent through the post to prospective customers; also attributive.

material dispatched to potential customers as part of an advertising campaign.

victory mail (see quot. 1966).

mail conveyed by sea; a service for conveying letters, parcels, etc., by sea (not an official term); so as v. transitive (rare), to send by sea; cf…

(a) propaganda sent by post promoting hatred or hostility towards a particular social group, faith, etc.; (b) letters or emails containing hostile…

(U.S.), mail sent by a system of recorded delivery (see recorded delivery n. at recorded, adj. compounds); the system itself.

A proprietary name for: a system of sending messages whereby the text of a message is transmitted to a post office near its ultimate destination…