blue box

noun

Definition of blue box

: an electronic device attached to a telephone that emits signals enabling the user to make illegal free long-distance calls

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First Known Use of blue box

1965, in the meaning defined above

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The first known use of blue box was in 1965

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Cite this Entry

“Blue box.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/blue%20box. Accessed 7 Aug. 2020.

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