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a. Lacking intelligence; stupid or empty-headed.
b. Devoid of substance or meaning; vapid or inane: a vacuous comment.
c. Devoid of expression; vacant: a vacuous stare. See Synonyms at empty.
2. Lacking serious purpose or occupation; idle: "A sleepless night was followed by a vacuous day" (Zon Ferraris).
3. Archaic Devoid of matter; empty: vacuous space.

[From Latin vacuus, empty; see vacuum.]

vac′u·ous·ly adv.
vac′u·ous·ness n.
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
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Adv.1.vacuously - in a vacuous manner
Based on WordNet 3.0, Farlex clipart collection. © 2003-2012 Princeton University, Farlex Inc.
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References in classic literature ?
It is my contemptible weakness that if I say a character smiled vacuously, I must smile vacuously; if he frowns or leers, I frown or leer; if he is a coward or given to contortions, I cringe, or twist my legs until I have to stop writing to undo the knot.
The cook turned his watery blue eyes upon Rokoff and smiled vacuously.
As a preliminary to another journey to his bunk, he hooked Wolf Larsen's buttonhole with a greasy forefinger and vacuously proclaimed and reiterated, "I got money, I got money, I tell yer, an' I'm a gentleman's son."
The longstanding philosophical orthodoxy on counterfactuals holds, in part, that counterfactuals with metaphysically impossible antecedents ("counterpossibles") are indiscriminately vacuously true.
'Parties' which appear to consist of actors desperate for a new job posing vacuously on a red carpet, followed by industrial air kissing with people they'd avoid on the bus in the real world.
On his part the Indian High Commissioner vacuously thinks India 'gave' Buddhism to SL.
Therefore, it is ideal for a person to act vacuously in the comforts of their own abode but contrary in public settings.
And for the old ones, it meant sitting on the towering Kothari bandstand, keenly watching the crowds at play or perched on the Clifton wall, staring vacuously at the strong waves breaking on the stones.
We chatted vacuously about her for most of an hour and then she arranged the lips into a smile of sorts saying, 'We'll go Dutch on this right?
At one extreme, these assets are vacuously subjected to the general secured transactions rules established for all other intangibles, generating an unsatisfactory regime that fails to cater to the idiosyncrasies of the legal regime of IP licenses.
(24) Say we accept any theory that holds that a counterfactual is vacuously true if its antecedent is necessarily false.
Instead the gesture of welcoming scholars from the Americas has been repeated compulsively yet vacuously like the movement of a broken needle stuck in a groove--each reiteration producing a hiccupped snippet of masked imperial ideology, a chilling sound that has echoed through the AMS and SAM for almost a century.