vacuum tube

noun
1.
Also called, especially British, vacuum valve. an electron tube from which almost all air or gas has been evacuated: formerly used extensively in radio and electronics.
2.
a sealed glass tube with electrodes and a partial vacuum or a highly rarefied gas, used to observe the effects of a discharge of electricity passed through it.

Origin:
1775–85

Dictionary.com Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
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Collins
World English Dictionary
vacuum tube or vacuum valve
 
n
another name for valve
 
vacuum valve or vacuum valve
 
n

Collins English Dictionary - Complete & Unabridged 10th Edition
2009 © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009
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American Heritage
Science Dictionary
vacuum tube  
An electron tube from which all air has been removed. The vacuum ensures transparency inside the tube for electric fields and moving electrons. Most electron tubes are vacuum tubes; cathode-ray tubes, which include television picture tubes and other video display tubes, are the most widely used vacuum tubes. In other electronic applications, vacuum tubes have largely been replaced by transistors.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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FOLDOC
Computing Dictionary

vacuum tube definition


electron tube

The Free On-line Dictionary of Computing, © Denis Howe 2010 http://foldoc.org
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Encyclopedia Britannica
Encyclopedia

vacuum tube

device usually consisting of a sealed glass or metal-ceramic enclosure that is used in electronic circuitry to control a flow of electrons. Among the common applications of vacuum tubes are amplification of a weak current, rectification of an alternating current (AC) to direct current (DC), generation of oscillating radio-frequency (RF) power for radio and radar, and creation of images on a television screen or computer monitor. Common types of electron tubes include magnetrons, klystrons, gyrotrons, cathode-ray tubes (such as the thyratron), photoelectric cells (also known as phototubes), and neon and fluorescent lamps.

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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Example sentences
These new computers will eventually make a stand-alone desktop system look as
  anachronistic as the vacuum tube.
Vacuum tube hardware weighing hundreds of kilograms is needed to produce the
  highest-power signals for military radar.
They are coupled to opposite ends of the same motor, the speed of which is held
  constant by means of a vacuum tube regulator.
Xenon in a vacuum tube produces a beautiful blue glow when excited by an
  electrical discharge.
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