In Hungarian printing jargon, the term poloska refers to a random printing flaw caused by a small foreign particle between the printing surface and the paper. It usually appears as a local area of missing print.

The phenomenon is especially associated with offset printing. Because the position of the foreign material is accidental, the flaw generally appears on only one or a few consecutive stamps and does not recur consistently in the same sheet position as a true plate flaw would.

Older Hungarian literature sometimes used the term “moon” for circular, dot-shaped or ring-shaped examples of this type. Today the printer's slang term poloska is more commonly used among Hungarian collectors. Such flaws are usually not major rarities and generally add only modest value, but many collectors actively look for these accidental printing curiosities.