Definition of acid in English:


Line breaks: acid
Pronunciation: /ˈasɪd


  • 1A substance with particular chemical properties including turning litmus red, neutralizing alkalis, and dissolving some metals; typically, a corrosive or sour-tasting liquid of this kind: trees were exposed to mixtures of heavy metals, acids, and overdoses of nutrients [mass noun]: traces of acid Often contrasted with alkali and base1.
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    • It can withstand high temperatures and is resistant to many corrosive substances such as acids and alkalis.
    • Zinc is a fairly active metal that dissolves in both acids and strong alkalis.
    • Copper is a moderately reactive metal that dissolves in most acids and alkalis.
  • 1.1 [mass noun] Bitter or cutting remarks or tone of voice: she was unable to quell the acid in her voice
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    • The bitterness and acid in his voice reassured me Peter was still in there, but he was very, very upset.
    • I guess I hadn't spoken with such acid in my tone for a while.
    • Her tone lacked its previous acid; she almost sounded sincere.
  • Acids are compounds which release hydrogen ions (H+) when dissolved in water. Any solution with a pH of less than 7 is acidic, strong acids such as sulphuric or hydrochloric acid having a pH as low as 1 or 2

  • 2 Chemistry A molecule or other species which can donate a proton or accept an electron pair in reactions.
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    • They would like to use their carborane acids to bind protons to atoms of the inert gas xenon.
    • Weak acids have dissociable protons like strong acids, but they simply do not dissociate completely.
    • The acid's active ingredient is positively charged hydrogen, so a transfer of electrons takes place between the zinc and the acid.
  • 3 [mass noun] informal The drug LSD: she didn’t have a clue the sweet had acid in it [as modifier]: a bad acid trip
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    • He has used mescaline, cocaine and acid, although he has not indulged in intravenous drugs.
    • He looked around more, seeing many different things that he would never expect: cocaine, meth and acid.
    • That heroin and acid were and are illegal didn't seem to stop him.


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  • 1Containing acid or having the properties of an acid; having a pH of less than 7: acid soils Often contrasted with alkaline or basic.
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    • In the case of acid soils, burning decreases acidity, which starts to increase again during the planting period.
    • Boxwood prefer slightly acid to slightly alkaline soil and do very well when planted in early fall.
    • It used to be that, if you had a very acid soil, the hydrangeas would be bluer; more alkaline soil, your hydrangeas would be pinker.
  • 3 Geology (Of rock, especially lava) containing a relatively high proportion of silica: the magma may start off fairly basic and end up at the close of the eruption much more acid
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    • Acraman occurs in the Gawler Range Volcanics, a Mesoproterozoic continental suite of mainly acid lavas and ash flows.
    • In the Southern Central Iberian Zone there are minor acid volcanic rocks intercalated with Caradoc-Ashgill limestones.
    • These deposits are intimately associated with the porphyric parts of intermediate to acid plutons in orogenic belts.
  • 3.1 Metallurgy Relating to or denoting steel-making processes involving silica-rich refractories and slags: the acid Bessemer process
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    • In the acid processes, deoxidation can take place in the furnaces, leaving a reasonable time for the inclusions to rise into the slag and so be removed before casting.
    • Therefore, a business opportunity could be created for an entrepreneur interested in running the acid separation and purification process.
    • As it happened, Workington's adherence to acid steelmaking sealed the fate of the ore dock in the next few years.


put the acid on

Australian /NZ informal Seek to extract a loan or favour from (someone).
[acid from acid test, referring to possible resistance (because gold resists nitric acid)]
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  • Plans to erect fences around those sectors are underway with Labor Council likely to put the acid on at least 12 Sydney-based councils in the near future.
  • A building inspector, put the acid on a builder for initially $40,000, but reduced it to $20,000 and then foolishly took two cheques each for $10,000.
  • Labour Council will put the acid on the Environment Minister to fund training for delegates and organisers about how they can utilise existing legislation to become frontline environmental watchdogs.



More example sentences
  • The grilled lemon chicken special was great, and showed that the chef has real skill - there's nothing better than the blend of acidy lemon with a bit of charred poultry.
  • The taste changes to become sweet and a little acidy.
  • There's homemade tzatziki with everything, and it's acidy and flavourful.


early 17th century (in the sense 'sour-tasting'): from Latin acidus, from acere 'be sour'.

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Pronunciation: ˌkɒlərəˈtjʊərə
elaborate ornamentation of a vocal melody