1
: a sour substance
specifically
: any of various typically water-soluble and sour compounds that in solution are capable of reacting with a base (see base entry 1 sense 6a) to form a salt, redden litmus, and have a pH less than 7, that are hydrogen-containing molecules or ions able to give up a proton to a base, or that are substances able to accept an unshared pair of electrons from a base
2
: something incisive, biting, or sarcastic
a social satire dripping with acid
3
: lsd
acidy
adjective
ˈa-sə-dē
1
a
: sour, sharp, or biting to the taste
an acid flavor
b
: sharp, biting, or sour in manner, disposition, or nature
an acid individual
an acid personality
c
: sharply clear, discerning, or pointed
an acid wit
acid criticism
d
: piercingly intense and often jarring
acid yellow
2
a
: of, relating to, or being an acid
also
: having the reactions or characteristics of an acid
acid soil
an acid solution
b
of salts and esters
: derived by partial exchange of replaceable hydrogen
acid sodium carbonate NaHCO3
c
: containing or involving the use of an acid (as in manufacture)
an acid bath
d
: marked by or resulting from an abnormally high concentration of acid
acid indigestion
3
: relating to or made by a process in which the furnace is lined with acidic material and an acidic slag is used
acid steel
4
: rich in silica
acid rocks
acidly
adverb
acidness
noun
Synonyms
Examples of acid in a Sentence
Noun
the acids in your stomach
the kinds of acid found in your stomach
Adjective
He washes his windows with an acid solution of vinegar and water.
with her acid personality, my aunt could be relied upon to bring some much-needed balance to the holiday gush
Recent Examples on the Web
Devra Ferst, Bon Appétit, 11 Apr. 2024
Unlike the aforementioned alpha-hydroxy acids, tranexamic acid isn't a chemical exfoliator, but a synthetic derivative of the amino acid lysine.
—Jennifer Hussein, Allure, 10 Apr. 2024
Earthjustice has also cited past incidents at the Santa Fe Springs facility in which ammonia and hydrochloric acid had been released at the site and workers had been burned with acid.
—Emily Alpert Reyes, Los Angeles Times, 9 Apr. 2024
Take supplements: Folic acid helps protect against birth defects.
—Wendy Wisner, Health, 27 Mar. 2024
This exfoliating face mask is enriched with glycolic acid and mandelic acid to slough off dry, dead skin cells and target the complexion’s overall appearance.
—Jessie Quinn, Peoplemag, 25 Mar. 2024
The acid decays the tooth, but also destroys DNA and stops the dental plaque from fossilizing and hardening over time.
—Laura Baisas, Popular Science, 27 Mar. 2024
Another option is to neutralize the acid on site using alkaline minerals such as olivine or basalt.
—IEEE Spectrum, 26 Mar. 2024
In addition to potent acids, the treatment also has pumpkin, papaya, and pineapple enzymes for additional exfoliating power.
—Jessie Quinn, Peoplemag, 25 Mar. 2024
Leslie Felperin, The Hollywood Reporter, 4 Apr. 2024
The jabs were sometimes playful, sometimes acid, often overstated.
—Noah Bierman, Los Angeles Times, 27 Mar. 2024
Ebb Carbon’s process makes seawater more alkaline and locks away carbon dioxide but generates some acid waste.
—IEEE Spectrum, 26 Mar. 2024
Acid reflux is what happens when acid from your stomach repeatedly rises into your esophagus.
—Daryl Austin, USA TODAY, 22 Feb. 2024
For instance, one of the key functions of the skin microbiota, which are mostly bacteria, is acid resistance.
—Sabrina Sholts, Smithsonian Magazine, 12 Mar. 2024
Freeman acquired the sculpture, which is acid bright and nearly six feet tall, from Schütte’s show that same year at Galerie Nelson in Paris.
—Travis Diehl Dean Kaufman, New York Times, 11 Mar. 2024
Kremlin spokesman Dmitry Peskov, replied with acid snark — accusing accused Kyiv of killing its own soldiers.
—Siobhán O'Grady, Washington Post, 25 Jan. 2024
Earlier ripening means more acid and fresher flavors in our wines.
—Mike Desimone and Jeff Jenssen, Robb Report, 23 Jan. 2024
Noun
Try teal spirals or striped acid yellow tapers in silver candleholders topped with jade rings or pale blue ones that look like large format rigatoni bent into interesting shapes.
—Devra Ferst, Bon Appétit, 11 Apr. 2024
Unlike the aforementioned alpha-hydroxy acids, tranexamic acid isn't a chemical exfoliator, but a synthetic derivative of the amino acid lysine.
—Jennifer Hussein, Allure, 10 Apr. 2024
Earthjustice has also cited past incidents at the Santa Fe Springs facility in which ammonia and hydrochloric acid had been released at the site and workers had been burned with acid.
—Emily Alpert Reyes, Los Angeles Times, 9 Apr. 2024
Take supplements: Folic acid helps protect against birth defects.
—Wendy Wisner, Health, 27 Mar. 2024
This exfoliating face mask is enriched with glycolic acid and mandelic acid to slough off dry, dead skin cells and target the complexion’s overall appearance.
—Jessie Quinn, Peoplemag, 25 Mar. 2024
The acid decays the tooth, but also destroys DNA and stops the dental plaque from fossilizing and hardening over time.
—Laura Baisas, Popular Science, 27 Mar. 2024
Another option is to neutralize the acid on site using alkaline minerals such as olivine or basalt.
—IEEE Spectrum, 26 Mar. 2024
In addition to potent acids, the treatment also has pumpkin, papaya, and pineapple enzymes for additional exfoliating power.
—Jessie Quinn, Peoplemag, 25 Mar. 2024
Adjective
Sadly, this latest Scoop has none of Waugh’s acid wit or alkaline intelligence.
—Leslie Felperin, The Hollywood Reporter, 4 Apr. 2024
The jabs were sometimes playful, sometimes acid, often overstated.
—Noah Bierman, Los Angeles Times, 27 Mar. 2024
Ebb Carbon’s process makes seawater more alkaline and locks away carbon dioxide but generates some acid waste.
—IEEE Spectrum, 26 Mar. 2024
Acid reflux is what happens when acid from your stomach repeatedly rises into your esophagus.
—Daryl Austin, USA TODAY, 22 Feb. 2024
For instance, one of the key functions of the skin microbiota, which are mostly bacteria, is acid resistance.
—Sabrina Sholts, Smithsonian Magazine, 12 Mar. 2024
Freeman acquired the sculpture, which is acid bright and nearly six feet tall, from Schütte’s show that same year at Galerie Nelson in Paris.
—Travis Diehl Dean Kaufman, New York Times, 11 Mar. 2024
Kremlin spokesman Dmitry Peskov, replied with acid snark — accusing accused Kyiv of killing its own soldiers.
—Siobhán O'Grady, Washington Post, 25 Jan. 2024
Earlier ripening means more acid and fresher flavors in our wines.
—Mike Desimone and Jeff Jenssen, Robb Report, 23 Jan. 2024
These examples are programmatically compiled from various online sources to illustrate current usage of the word 'acid.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.
Word History
Etymology
Noun
borrowed from Medieval Latin acidum, going back to Latin, neuter of acidus acid entry 2
Adjective
borrowed from French & Latin; French acide, going back to Middle French, borrowed from Latin acidus, adjective derivative from the base of acēre "to be sour" — more at acetic acid
Phrases Containing acid
Articles Related to acid
Dictionary Entries Near acid
Cite this Entry
“Acid.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/acid. Accessed 19 Apr. 2024.
Copy Citation
Kids Definition
acid
2 of 2 noun1
: a sour substance
2
: a compound that usually dissolves in water, has a sour taste, reacts with a base to form a salt, and turns litmus paper red
3
: lsd
Medical Definition
acid
1 of 2 noun1
: a sour substance
specifically
: any of various typically water-soluble and sour compounds that in solution are capable of reacting with a base (see base sense 3a) to form a salt, redden litmus, and have a pH less than 7, that are hydrogen-containing molecules or ions able to give up a proton to a base, or that are substances able to accept an unshared pair of electrons from a base
2
: lsd
acid
2 of 2 adjective
ac·id
ˈas-əd 
1
: sour, sharp, or biting to the taste
2
a
: of, relating to, or being an acid
also
: having the reactions or characteristics of an acid
an acid solution
b
of salts and esters
: derived by partial exchange of replaceable hydrogen
acid sodium carbonate NaHCO3
c
: marked by or resulting from an abnormally high concentration of acid
acid indigestion
see also acid reflux
More from Merriam-Webster on acid
Nglish: Translation of acid for Spanish Speakers
Britannica English: Translation of acid for Arabic Speakers
Britannica.com: Encyclopedia article about acid
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