Definition of caustic in US English:



  • 1Able to burn or corrode organic tissue by chemical action.

    ‘a caustic cleaner’
    • ‘It is done at high temperatures with caustic chemicals in factory conditions.’
    • ‘The list includes sodium hydroxide and potassium hydroxide, caustic chemicals that will rip the skin off your fingers and the lining from the throat.’
    • ‘Alkaline substances did not have a sour taste but were caustic and felt slippery.’
    • ‘It is also the opposite of baking and washing soda; it is acidic and therefore neutralizes alkaline or caustic substances.’
    • ‘Regeneration of this resin is by a caustic brine solution.’
    • ‘Some of the chemicals - including caustic hydrogen fluoride and deadly arsine gas - are toxic, and the fossil fuel consumed contributes to global warming, says Williams.’
    • ‘The process is relatively simple, although the chemicals required are caustic and need to be handled carefully.’
    • ‘The caustic burn was treated successfully, and the patient eventually achieved good vision after uncomplicated cataract surgery.’
    • ‘Because alkaline strippers are so caustic, great care must also be taken during their application.’
    • ‘When these materials burn, they release dense smoke and toxic fumes, such as hydrogen cyanide and carbon monoxide, which are caustic to skin and eyes and can be lethal if inhaled.’
    • ‘Never use caustic household chemicals to clean your leather items.’
    • ‘This pollutant can be absorbed by both your lungs and your skin and result in caustic burns, kidney and liver damage and hyperactivity.’
    • ‘Others may contain noxious or caustic materials that could burn the mucous membranes of the mouth.’
    • ‘It may be worth noting that because caustic chemicals are used in hair dyes, perms, and relaxers, you would be wise to place your hair in the hands of a professional.’
    • ‘Therefore, be very careful to keep caustic chemicals away from skin and eyes and wear protective clothing.’
    • ‘Now you can use anti-freeze or salts to lower the melting point, but you can only go so far with that and still allow life to exist, otherwise the chemicals become too caustic.’
    • ‘Lye is hazardous, very caustic, and will burn skin.’
    • ‘Sodium hydroxide is a caustic type of chemical that actually softens hair fibers.’
    • ‘Concentrated acids and caustic alkalis should be handled with the greatest care.’
    • ‘Initially firefighters used hand-held jets to tackle the blaze while experts established that four different chemicals were involved that were caustic and could cause burns.’
    corrosive, corroding, mordant, acid, alkaline, burning, stinging, acrid, harsh, destructive
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  • 2Sarcastic in a scathing and bitter way.

    ‘the players were making caustic comments about the refereeing’
    • ‘He had been a serious, shy young man whose wit showed only in the bitterly caustic cartoon strips he drew, the strips that were rejected by paper after paper.’
    • ‘When they pulled out of NATO 40 years ago Secretary of State Dean Rusk had a bitterly caustic response.’
    • ‘In 1890 he published The Gentle Art of Making Enemies, a collection of caustic letters and comment.’
    • ‘She's been compared to Eminem for caustic wordplay that would sound awesome atop some straight hip-hop, but that would be too easy.’
    • ‘Throughout the trial he evinced a range of carefully calibrated emotions - caustic, sarcastic, disbelieving and, at this moment, outraged.’
    • ‘He'd left that after an hour of wandering around, trying not to sound too caustic in his comments about the whole thing.’
    • ‘The show is a delightful, gin-soaked celebration of the work of Dorothy Parker, legendary American critic, columnist and queen of caustic wit.’
    • ‘I am continually surprised by Sharon's creativity even if it is currently directed towards caustic but witty sarcasm.’
    • ‘Joel had to bite back the caustic remark that burned on the tip of his tongue.’
    • ‘This awareness lends even the most caustic social commentary additional gravity, or sadness.’
    • ‘One of the most caustic comments on the present-day globalisation has come from Robert Samuelson in the Newsweek of February 24.’
    • ‘She was a caustic critic of charismatic ministers who speechify but don't mobilize.’
    • ‘Her caustic, waspish comments on the other housemates were biting and bitchy, but always spot on.’
    • ‘He is equally caustic about Western art historians and critics.’
    • ‘As Ireland missed three times from the penalty spot and Spain took advantage, the first caustic comment on the team's performance came from former local soccer star Tom Lambert.’
    • ‘Revered by many of today's generation of poets, Stephens was generally considered a spoken word pioneer, not to mention an often caustic literary critic for the Mirror.’
    • ‘She was attacked in 1930 by the caustic critic Wyndham Lewis for her ‘fashionable dimness‘.’
    • ‘It's more irreverent, sarcastic, and caustic than what I'm used to hearing from Army officer wives I knew - and female Army officers in dual-military couples.’
    • ‘The pattern of caustic complaints and sarcastic responses slowly gave way to a new pattern of care toward one another.’
    • ‘She's really quite funny, in a bitter, caustic kind of way.’
    sarcastic, cutting, biting, mordant, stinging, sharp, bitter, scathing, derisive, sardonic, ironic, scornful, trenchant, acerbic, vitriolic, tart, acid, pungent, acrimonious, astringent, rapier-like, razor-edged, critical, polemic, virulent, venomous, waspish
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  • 3Physics
    Formed by the intersection of reflected or refracted parallel rays from a curved surface.

    • ‘For example they worked together on caustic curves during 1692-93 although they did not publish the work jointly.’
    • ‘Sturm's theoretical work in mathematical physics involved the study of caustic curves, and poles and polars of conic sections.’
    • ‘He also investigated caustic curves and in particular he studied these associated curves of the parabola, the logarithmic spiral and epicycloids around 1692.’
    • ‘In On burning mirrors Diocles also studies the problem of finding a mirror such that the envelope of reflected rays is a given caustic curve or of finding a mirror such that the focus traces a given curve as the Sun moves across the sky.’
    • ‘The lower right has a metal ring with a caustic reflection.’


  • 1A caustic substance.

    • ‘Production is potentially dangerous, as you need to heat volatile methanol with caustics.’
    • ‘Spent grain, yeast, ethanol, and acids and caustics used for cleaning are all sent out to be used for feed for cattle or reprocessed and reused industrially.’
    • ‘The scenes below show caustics, which are very difficult to render.’
    • ‘Aughinish jetty receives ore, oil and caustic and exports the finished aluminium oxide.’
    • ‘Loam and caustic might be thought of as the conditions of existence: the one an especially fertile soil, life-giving; the other a burning substance that destroys living tissue.’
  • 2Physics
    A caustic surface or curve.

    • ‘The caustic of a circle with radiant point on the circumference is a cardioid, while if the rays are parallel then the caustic is a nephroid.’
    • ‘The caustic of the tricuspoid, where the rays are parallel and in any direction, is an astroid.’
    • ‘However with ray tracing, shadow mapping, radiosity, and caustics, an algorithm to compute light reflected from curved or transparent surfaces, it is easy to create multi-layered soft lights and shadows in LightWave.’
    • ‘Nevertheless, this elucidation of the generic discontinuous change has shed light upon many optical phenomena where caustics and diffraction occur.’
    • ‘The caustic of the equiangular spiral, where the pole is taken as the radiant, is an equal equiangular spiral.’


Late Middle English: via Latin from Greek kaustikos, from kaustos ‘combustible’, from kaiein ‘to burn’.