(historical) The letter "A" in scarlet cloth required to be worn by those convicted of adultery in 17th-century Puritan New England.

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

An aerogram; a letter sent by airmail.

(US) Alternative spelling of Greek-letter

(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.

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

Exactly correct, correct in every letter.

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”).