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.
A court filing described pentobarbital as a caustic substance that burns skin, tissue and veins.
From Barron's ● Oct. 7, 2026
While your brother-in-law’s behavior does sound a bit caustic, at least by your retelling, I urge you to de-center yourself.
From MarketWatch ● Sep. 24, 2026
Gaulier snorted, a rare sign of approval from the exacting clown instructor, who was known for his blunt critiques and caustic insults.
From The Wall Street Journal ● Aug. 26, 2026
The BBC Two series was too caustic to last for more than two seasons.
From Salon ● Jun. 12, 2026
The next day the newspaper singled out Chauncey Depew, president of the New York Central, for a particularly caustic appraisal.
From "The Devil in the White City" by Erik Larson
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.
