window envelope

American  

noun

1. an envelope with a transparent opening through which the address on the enclosure may be read.

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window envelope British  

noun

1. a type of envelope, esp for business use, having a transparent area that reveals the address within

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Etymology

Origin of window envelope

First recorded in 1915–20

Example Sentences

Aetna said it "confirmed that the vendor handling the mailing had used a window envelope, and, in some cases, the letter could have shifted", allowing personal information to be seen.

From BBC

If window envelopes are used the window should be clear, the paper white or nearly so, and the typewritten address a good honest black.

From Project Gutenberg