acid

From French acide, from Latin acidus (“sour, acid”), from aceō (“to be sour”). Doublet of agita.

• (Received Pronunciation, General American) enPR: ăs'ĭd, IPA^(key): /ˈæsɪd/

• Audio (General American):

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• Audio (General American):

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• Rhymes: -æsɪd

acid (comparative acider, superlative acidest)

1. Sour, sharp, or biting to the taste; tart; having the taste of vinegar.

   acid fruits or liquors

2. (figuratively) Sour-tempered.

   His response was harsh and acid.

   • 1864, Anthony Trollope, The Small House at Allington, 2nd edition, volume 2, Smith, Elder & Co., page 235:

     His voice was as stern and his face as acid as ever.

   • 1912, Arthur Conan Doyle, The Lost World […], London; New York, N.Y.: Hodder and Stoughton, →OCLC:

     It must be admitted that Challenger is provocative in the last degree, but Summerlee has an acid tongue, which makes matters worse.

   • 1914 November, Louis Joseph Vance, “An Outsider […]”, in Munsey’s Magazine, volume LIII, number II, New York, N.Y.: The Frank A[ndrew] Munsey Company, […], published 1915, →OCLC, chapter I (Anarchy), page 373, column 2:

     Little disappointed, then, she turned attention to "Chat of the Social World," gossip which exercised potent fascination upon the girl's intelligence. She devoured with more avidity than she had her food those pretentiously phrased chronicles of the snobocracy—[…]—distilling therefrom an acid envy that robbed her napoleon of all its flavor.

3. Of or pertaining to an acid; acidic.

   acid soils

   • 1975, Peter N. Barber, Cecil Ernest Lucas Phillips, The Trees Around Us, page 101:

     Like other nyssas, it is in nature a creature of swampy places and looks loveliest where massed close to water and reflected in it, but justifies itself elsewhere if the soil is moist and acid, succeeding in wet clay.

4. (music) Denoting a musical genre that is a distortion (as if hallucinogenic) of an existing genre, as in acid house, acid jazz, acid rock.

• For quotations using this term, see Citations:acid.

• acidic

• alkaline
• base

acid (countable and uncountable, plural acids)

1. A sour substance.
2. (chemistry)
   1. Any compound which yields H+ ions (protons) when dissolved in water; an Arrhenius acid.
      • 2015 August 18, Clelia De-la-Peña et al., “The role of chromatin modifications in somatic embryogenesis in plants”, in Frontiers in Plant Science‎^[1], volume 6, →DOI:

        SE onset depends on a complex network of interactions among plant growth regulators, mainly auxins and cytokinins, during the proembryogenic early stages, and ethylene and gibberellic and abscisic acids later in the development of somatic embryos.

   2. Any compound that easily donates protons to a base; a Brønsted acid.
   3. Any compound that can accept a pair of electrons to form a covalent bond; a Lewis acid.
3. Any corrosive substance.
   • 2006, James Fenton, Jerusalem:

     You are in error. / This is terror. / This is your banishment. This land is mine. / This is what you earn. / This is the Law of No Return. / This is the sour dough, this the sweet wine. / This is my history, this my race / And this unhappy man threw acid in my face.

4. (uncountable, slang) LSD, lysergic acid diethylamide.
   • 1967, Joe David Brown, editor, The Hippies, New York: Time, Inc, page 171:

     In the end, though, there is one sure way to distinguish a real hippie from his assorted sympathizers: hippies drop acid. That is, real hippies frequently, if irregularly, ingest LSD.

• alkali
• base

• See also Thesaurus:acid/Hyponyms

• → Welsh: asid

• acerbic
• acro-
• pH

• “acid”, in Webster’s Revised Unabridged Dictionary, Springfield, Mass.: G. & C. Merriam, 1913, →OCLC.

• -adic, Daic, adic, cadi, caid

acid m (plural acide, definite acidi, definite plural acidet)

1. (chemistry) acid

   Synonym: thartor

• FGJSSH: Fjalor i gjuhës së sotme shqipe [Dictionary of the modern Albanian language]‎^[2], 1980
• “acid”, in FGJSH: Fjalor i gjuhës shqipe [Dictionary of the Albanian language] (in Albanian), 2006

Unadapted borrowing from English acid.

Attested since at least 1970.

• Audio:

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acid m (uncountable, no diminutive)

1. (slang) LSD, lysergic acid diethylamide

   Synonym: LSD

2. (music) acid

Borrowed from French acide, from Latin acidus (“sour, acid”).

• IPA^(key): [aˈt͡ʃid]

acid m or n (feminine singular acidă, masculine plural acizi, feminine/neuter plural acide)

1. acid, acidic

• aciditate

acid m (plural acizi)

1. acid

• acid dezoxiribonucleic

• “acid”, in DEX online—Dicționare ale limbii române (Dictionaries of the Romanian language) (in Romanian), 2004–2026

• IPA^(key): /ˈaθid/ [ˈa.θið̞] (Equatorial Guinea, Spain)
• IPA^(key): /ˈasid/ [ˈa.sið̞] (Latin America, Philippines)
• Rhymes: -aθid (Equatorial Guinea, Spain)
• Rhymes: -asid (Latin America, Philippines)
• Syllabification: a‧cid

acid (invariable)

1. (music) acid

acid m (uncountable)

1. (music) acid

• “acid”, in Diccionario de la lengua española [Dictionary of the Spanish Language] (in Spanish), online version 23.8.1, Royal Spanish Academy [Spanish: Real Academia Española], 15 December 2025