Definitive stamp - A postage stamp intended to remain in everyday use for a considerable time, as distinct from provisional, commemorative or other special issues.

Demonetized - No longer legal tender; in particular, a postage stamp bearing a duty in an obsolete system of currency, or of an issue stated by the postal authority to be no longer valid for postage.

Die - The original single engraved piece of metal from which a multiple-printing plate is built up.

Die proof - Single, very carefully impressed proof of a new postage stamp die, invariably in black ink on smooth white card or fine-calendered or coated paper. When dry, inspected in great detail to check that the die is perfect.

Dirhem - Old Turkish weight unit of about 3.2 grams.

Disaster Mail - (Crash Mail) A philatelic term for a type of cover, (including the terms air accident cover, interrupted flight cover, wreck cover) meaning an envelope or package that has been recovered from an aircraft, airship or airplane crash, train wreck, shipwreck or other accident. Crash covers are a type of interrupted mail.

Discount stamps - As of December 1908, the Turkish post sold stamps with a discount of 20% in order to promote the use of the Turkish post against the Foreign post offices; the stamps were overprinted with the Arabic letter B, and from 1914 the overprint was a star.

Disinfected mail - or fumigated mail - Mail that has had some form of disinfection or fumigation applied to it by postal authorities, with the intention of preventing the spread of epidemics via letters sent from infected areas. The usual practice was to puncture the envelope with small holes, often in a grid pattern, or to cut a few short slits in the letter, in order to let the fumigation gases in. In addition, a special postal marking may note the disinfection process.

DLO - (Dead Letter Office) - RLD (Return Letter Department), RLO (Return Letter Office) - The postal office where undeliverable mail, that cannot be delivered to the addressee or returned to the sender, ends its journey. This is usually due to lack of compliance with postal regulations, an incomplete address and return address, or the inability to forward the mail when both correspondents move before the letter can be delivered. Largely based on the British model that emerged in the late eighteenth century, many countries developed similar systems for processing undeliverable mail.

Double circle postmark - A circular date handstamp contained within two concentric circles.

Double impression - Two impressions of the same stamp resulting from the sheet being run through the press twice.

Drucksachen - (German) Items of printed matter.

Dry print - Postage stamp image or overprint grossly deficient in ink, but not albino (which is devoid of any ink).

Dumb cancellation - An obliteration handstamp containing neither figure nor letter, often made of cork. Used for a variety of purposes including: cancellation of postage stamps (Maltese cross); wartime security cancelling, and more.