caustic
Americanadjective
noun
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a caustic substance.
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Optics.
adjective
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capable of burning or corroding by chemical action
caustic soda
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sarcastic; cutting
a caustic reply
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of, relating to, or denoting light that is reflected or refracted by a curved surface
noun
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Also called: caustic surface. a surface that envelops the light rays reflected or refracted by a curved surface
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Also called: caustic curve. a curve formed by the intersection of a caustic surface with a plane
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chem a caustic substance, esp an alkali
Other Word Forms
Etymology
Origin of caustic
1350–1400; Middle English < Latin causticus < Greek kaustikós burning, caustic, equivalent to kaust ( ós ) burnt (verbal adjective of kaíein to burn) + -ikos -ic
Explanation
Use the adjective caustic to describe any chemical that is able to burn living tissue or other substances, or, figuratively, a statement that has a similarly burning effect. Caustic in this sense means harshly critical. In the chemical sense, a near synonym is corrosive. In the figurative sense, near synonyms are biting, scathing, and sarcastic. The source of the word caustic is Latin causticus, from Greek kaustikos, from kaiein "to burn."
Vocabulary lists containing caustic
The SAT: Words to Capture Tone, List 1
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The New SAT: Words to Capture Tone
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100 Words to Make You Sound Smart
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Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
She’s forward and caustic, with a sharp wit and a hefty Jersey accent that doesn’t exactly scream “therapist’s office” — unless your therapist is Dr. Melfi from “The Sopranos,” in which case, lucky you.
From Salon • Apr. 29, 2026
Okrent portrays Sondheim as witty and endearing, but also poorly groomed, remote, caustic, quick to anger — and, mostly, quick to forgive.
From Los Angeles Times • Mar. 17, 2026
Around him orbits a constellation of classmates - caustic, thoughtful, restless - who debate Swiss-French architect Le Corbusier, Karl Marx and the price of cigarettes with equal seriousness.
From BBC • Feb. 13, 2026
Over the past 14 years, Warsh has been a consistent critic of the Fed, often in caustic terms.
From MarketWatch • Jan. 31, 2026
Dill met Brother McKinnon’s caustic gaze, his shame decaying into anger.
From "The Serpent King" by Jeff Zentner
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
