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

The federal investigators encountered puddles of crude oil on the facility grounds, as well as caustic fumes emanating from the facility, resulting in violations for air quality and other environmental infractions.

From Los Angeles Times • Feb. 14, 2026

Over the past 14 years, Warsh has been a consistent critic of the Fed, often in caustic terms.

From MarketWatch • Jan. 31, 2026

Several people who have spoken with Warsh have been taken aback at the caustic nature of his criticisms of Fed leaders.

From The Wall Street Journal • Jan. 30, 2026

The civility of this encounter belied a caustic battle being waged outside Jackson Park for the rights to illuminate the exposition.

From "The Devil in the White City" by Erik Larson

Related Words

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