caustic

American  

[kaw-stik] / ˈkɔ stɪk /

adjective

1. capable of burning, corroding, or destroying living tissue.

2. severely critical or sarcastic.

   a caustic remark.

   Synonyms:

   acid, scathing, bitter, mordant, biting

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noun

1. a caustic substance.

2. Optics.

   1. caustic curve.

   2. caustic surface.

caustic British  

/ ˈkɔːstɪk, kɔːˈstɪsɪtɪ /

adjective

1. capable of burning or corroding by chemical action

   caustic soda

2. sarcastic; cutting

   a caustic reply

3. of, relating to, or denoting light that is reflected or refracted by a curved surface

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noun

1. Also called: caustic surface.  a surface that envelops the light rays reflected or refracted by a curved surface

2. Also called: caustic curve.  a curve formed by the intersection of a caustic surface with a plane

3. chem a caustic substance, esp an alkali

Other Word Forms

• caustical adjective
• caustically adverb
• causticity noun
• causticly adverb
• causticness noun
• noncaustic adjective
• noncaustically adverb
• overcaustic adjective
• overcaustically adverb
• overcausticity noun
• uncaustic adjective
• uncaustically adverb

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."

Example Sentences

Lyrical saint Nick Cave was more caustic — notoriously so — when he shared how he felt about these boys of California’s endless summer.

From Salon • Apr. 4, 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

At this point, you just don’t like each other, which makes communication feel even more caustic.

From MarketWatch • Feb. 27, 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

In the past when he walked out like that and sat looking over the country lying in just the faintest visible shape where the lost moon tracked the caustic waste he’d sometimes see a light.

From "The Road" by Cormac McCarthy

Related Words

• acerbic
• bitter
• harsh
• incisive
• pithy
• pungent
• satiric
• scathing
• sharp
• stinging
• trenchant