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thermionic valve

noun British.
  1. vacuum tube.
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Origin of thermionic valve

First recorded in 1915–20
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

British Dictionary definitions for thermionic valve

thermionic valve

esp US and Canadian thermionic tube

noun
  1. an electronic valve in which electrons are emitted from a heated rather than a cold cathode
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Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012