Definitive issue - a stamp issued in an indefinite quantity and for an indefinite period, usually several years or more. The United States presidential issue of 1938 and the 1995 32-cent Flag over Porch stamps are examples. Definitive stamp designs do not honor a specific time-dated event.
Dial (handstamp) - portion of a postmark that notes the city, date, and time
Die - the original engraving of a stamp design, usually recess-engraved in reverse on a small, flat sheet of soft steel. In traditional intaglio printing, a transfer roll is made from a die, and printing plates are made from impressions on the transfer roll. When more than one die is used in the production of an issue, distinctive variations are often identifiable.
Documentary stamp - a revenue stamp indicating payment of tax or fee on official or business document; overprinted to indicate use such as silver tax
Double entry - a term which refers to a visual characteristic on an engraved stamp such as partial doubling of the design due to misalignment of the transfer roll or over-rocking of a transfer roll which carries more than one design
Double impression - two impressions of the same stamp resulting from the sheet being run through the press twice
Double or triple perforation - a situation produced when a sheet is accidentally perforated more than once in the allotted space. This might result when the sheet is cut off center.
Dragging - the re-opening of lines for more color
Drop letter - mail to be delivered to an address within the same postal delivery area as the office in which it is posted. It is charged a lower postage rate.