ple·​num ˈple-nəm How to pronounce plenum (audio) ˈplē- How to pronounce plenum (audio)
: a space or all space every part of which is full of matter
: an air-filled space in a structure
especially : one that receives air from a blower for distribution (as in a ventilation system)
: a general assembly of all members especially of a legislative body
: the quality or state of being full

Examples of plenum in a Sentence

Recent Examples on the Web Yet no sooner had the plenum closed and the party released its initial communiqué than observers dismissed the meeting as a bust. Evan A. Feigenbaum, Foreign Affairs, 16 Dec. 2013 As if the drama in the Knesset and the fire on the streets weren’t enough, Netanyahu actually arrived at the Knesset plenum directly from a cardiac care unit. Jo-Ann Mort, The New Republic, 26 July 2023 Air is picked up by a four-inch-diameter duct just above the front air dam, flows unimpeded to the carburetor, where fuel is added, and then turns through 90 degrees in the plenum to enter the turbo compressor in a horizontal stream. Don Sherman, Car and Driver, 1 May 2023 The intake and exhaust plumbing has been smoothed out to improve airflow, and a plastic intake manifold replaces the former aluminum plenum equipped on manuals and features larger ports that feed a revised valvetrain. David Beard, Car and Driver, 17 Aug. 2021 Instead, there's a water jacket surrounding the plenum chamber. Don Sherman, Car and Driver, 1 May 2023 That’s because the engine wears a plastic cover that looks like a crinkle-finish intake plenum, so that is what is actually visible from outside the car. Dan Carney, Popular Science, 3 Apr. 2023 In the intervening week, Mr. Xi has concluded a major plenum of the Chinese Communist Party, which further entrenched his power. Kevin Rudd, WSJ, 12 Nov. 2021 Inside the plenum, as debate began, some opposition lawmakers stood and wrapped themselves in Israeli flags in protest. Isabel Kershner, New York Times, 20 Feb. 2023 See More

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'plenum.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History


borrowed from Latin plēnum, noun derivative from neuter of plēnus "full"; (sense 1a) after its use in the Lucullus book of Cicero's Academica to denote a space completely filled with matter (distinguished from ināne or vacuum "empty space"); (sense 2) apparently first from its use in Sweden in the eighteenth century to refer to a meeting of all members of the Riksdag — more at full entry 1

First Known Use

1678, in the meaning defined at sense 1a

Time Traveler
The first known use of plenum was in 1678

Dictionary Entries Near plenum

Cite this Entry

“Plenum.” Dictionary, Merriam-Webster, Accessed 11 Dec. 2023.

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