aerogram

(from the article `postal system`) For individual correspondence, the most practical and inexpensive form of airmail remains the compact aerogram, which was introduced in Britain ...
Found on http://www.britannica.com/eb/a-z/a/23

aerogram

aerogram 1. A roentgenogram of an organ afer it has been injected with air; also called pneumogram. 2. A letter designed for airmail consisting of a single sheet of lightweight paper that, once written on, can be folded and sealed to form an envelope.
Found on http://www.wordinfo.info/words/index/info/view_unit/2778/4

Aerogram

An Aerogram, Aérogramme or Air Letter is a thin lightweight piece of foldable and gummed paper for writing a letter for transit via airmail, in which the letter and envelope are one and the same. Most postal administrations forbid enclosures in these light letters, which are usually sent abroad at a preferential rate. Printed warnings existed to
Found on http://en.wikipedia.org/wiki/Aerogram
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