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English definition of “extension”

extension

noun [C] (PHONE)    /ɪkˈsten.ʃən/
B2 any of two or more phones in the same house that share the same number, or any of a number of phones connected to a switchboard in a large building such as an office: We have an extension in our bedroom. When you call, ask for extension 3276.Telephone equipment
(Definition of extension noun (PHONE) from the Cambridge Advanced Learner's Dictionary & Thesaurus © Cambridge University Press)
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