(dated) plural of woman of letters

(dated) female equivalent of man of letters

plural of nundinal letter

(now rare) A corporal with responsibility for carrying or delivering letters for a given regiment etc.

plural of letter corporal

(printing) Two letters on one shank; a ligature. / An item of mail requiring double postage.

A letter conveyed by a ship other than a mail packet.

plural of letter column

Section of a periodical in which readers' letters are published.

(dated, fandom slang) Correspondence, usually a letter, sent to a periodical commenting on either the contents of a previous issue or an earlier letter of comment.