Optical Character Reader (OCR)
Mail-processing machine, which reads an address and translates it into a sprayed-on barcode.
Omnibus Issues
A common theme used on the stamps of several different countries.
Orphelins de la Guerre (French)
War orphans
Oxidised
Term applied to a stamp, which has been darkened from sulphurisation or oxidation from age.
Oro Pastas (Lithuanian)
Air Post
Omnia Juncta in Uno (Latin)
All Joined in One
Original
A stamp from the first issue and not a reprint or later issue.
Olympische Spiele (German)
Olympic Games