(US) A letter mailed at a post office and either kept for general delivery, or delivered to a post office box, at that same post office.

A letter that is written generically with blanks to be filled in with individual details, often sent in bulk, and frequently regarded as impersonal.

An employee of the post office who delivers mail (post) to, and collects it from, a residence or business, or from public mailboxes.

An aerogram; a letter sent by airmail.

A knifelike device with a blunt edge, used for slicing letters open.

(nautical, historical) An official commission from a government authorizing someone to seize the property or people of another nation; especially to attack merchant shipping of another nation.

(Scotland, law) A letter passing the signet, whereby a debtor is relieved from personal diligence, or whereby an outlaw is reponed against sentence of outlawry.

an unsigned leaflet distributed clandestinely

(law) Rare form of letters patent (“a type of legal document in the form of an open letter issued by an authority granting a monopoly, right, status, or title to a person or organization”).

Printed to a sufficient visual standard to be sent as a letter.