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
Sarah Han, Allure, 28 Nov. 2023
The two-step anti-aging AHA/BHA pad is pre-dosed with five acids to visibly reduce dullness, uneven texture, pores and dark spots.
—Anna Tingley, Variety, 24 Nov. 2023
In interviews, some city sanitation workers described persistent safety concerns, such as coming into contact with carcasses of rabid dogs and acid splatter from batteries.
—Kurtis Lee, New York Times, 23 Nov. 2023
Its formula is made with patented Resorcinol Technology, glycolic acid, and tranexamic acid, which all work together to reduce dark spots and discoloration and brighten the skin in just 14 days.
—Rachel Simon, Peoplemag, 17 Nov. 2023
This production emphasizes — overly, in some places — the acid suspended in those charming rhymes.
—Jackson McHenry, Vulture, 31 Oct. 2023
Red onion and tomatoes provide acid while a sprinkling of cilantro freshens up what would otherwise be a heavy — and massive — taco.
—Kat Thompson, Los Angeles Times, 25 Oct. 2023
Antacids work by neutralizing stomach acid, while PPIs and H2 blockers reduce the amount of acid the stomach makes.
—Maggie O'Neill, Health, 16 Nov. 2023
Some grapes have naturally longer lifespans due to tannic structure and acid levels; in general, Cabernet Sauvignon has greater longevity than Pinot Noir.
—Mike Desimone and Jeff Jenssen, Robb Report, 5 Nov. 2023
Nardine Saad, Los Angeles Times, 7 Sep. 2023
Given that, acid chemical rust removers are best limited to removing rust from bare iron and steel.
—Tony Carrick, Popular Mechanics, 23 Mar. 2023
High levels of protein can increase acid production in urine, potentially leading to stone formation.
—Amber Smith, Discover Magazine, 10 Aug. 2023
For people with chronic acid reflux symptoms, healthcare providers may recommend PPIs for longer than 12 weeks.
—Maggie O'Neill, Health, 22 Aug. 2023
And while diet changes can help, Lakshminarayan told CNN that people suffering from acid reflux and heartburn should seek medical care.
—Cara Lynn Shultz, Peoplemag, 10 Aug. 2023
From the mountains and acid soils of the east to the inner Bluegrass to the western waterlands.
—Paul Cappiello, The Courier-Journal, 16 June 2023
Pressure canning uses steam to create high temperatures that kill microorganisms and pressure to seal jars filled with low acid foods like chicken stock or baked beans.
—Jonathan Bender, Popular Mechanics, 4 Aug. 2023
Acid Reflux When burping goes hand-in-hand with heartburn, acid reflux may be to blame.
—Karen Pallarito, Health, 27 July 2023
See More
Noun
If your skin is looking a little dull, these two products will brighten up your complexion à la tranexamic acid, niacinamide, and lotus seed extract (SkinMedica) or L-ascorbic acid and hyaluronic acid (Obagi Medical).
—Sarah Han, Allure, 28 Nov. 2023
The two-step anti-aging AHA/BHA pad is pre-dosed with five acids to visibly reduce dullness, uneven texture, pores and dark spots.
—Anna Tingley, Variety, 24 Nov. 2023
In interviews, some city sanitation workers described persistent safety concerns, such as coming into contact with carcasses of rabid dogs and acid splatter from batteries.
—Kurtis Lee, New York Times, 23 Nov. 2023
Its formula is made with patented Resorcinol Technology, glycolic acid, and tranexamic acid, which all work together to reduce dark spots and discoloration and brighten the skin in just 14 days.
—Rachel Simon, Peoplemag, 17 Nov. 2023
This production emphasizes — overly, in some places — the acid suspended in those charming rhymes.
—Jackson McHenry, Vulture, 31 Oct. 2023
Red onion and tomatoes provide acid while a sprinkling of cilantro freshens up what would otherwise be a heavy — and massive — taco.
—Kat Thompson, Los Angeles Times, 25 Oct. 2023
Antacids work by neutralizing stomach acid, while PPIs and H2 blockers reduce the amount of acid the stomach makes.
—Maggie O'Neill, Health, 16 Nov. 2023
Some grapes have naturally longer lifespans due to tannic structure and acid levels; in general, Cabernet Sauvignon has greater longevity than Pinot Noir.
—Mike Desimone and Jeff Jenssen, Robb Report, 5 Nov. 2023
Adjective
Peptic ulcers occur when acid in the digestive tract eats away at the inner surface of the stomach or small intestine, according to the Mayo Clinic.
—Nardine Saad, Los Angeles Times, 7 Sep. 2023
Given that, acid chemical rust removers are best limited to removing rust from bare iron and steel.
—Tony Carrick, Popular Mechanics, 23 Mar. 2023
High levels of protein can increase acid production in urine, potentially leading to stone formation.
—Amber Smith, Discover Magazine, 10 Aug. 2023
For people with chronic acid reflux symptoms, healthcare providers may recommend PPIs for longer than 12 weeks.
—Maggie O'Neill, Health, 22 Aug. 2023
And while diet changes can help, Lakshminarayan told CNN that people suffering from acid reflux and heartburn should seek medical care.
—Cara Lynn Shultz, Peoplemag, 10 Aug. 2023
From the mountains and acid soils of the east to the inner Bluegrass to the western waterlands.
—Paul Cappiello, The Courier-Journal, 16 June 2023
Pressure canning uses steam to create high temperatures that kill microorganisms and pressure to seal jars filled with low acid foods like chicken stock or baked beans.
—Jonathan Bender, Popular Mechanics, 4 Aug. 2023
Acid Reflux When burping goes hand-in-hand with heartburn, acid reflux may be to blame.
—Karen Pallarito, Health, 27 July 2023
See More
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 3 Dec. 2023.
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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