acid

noun

Definition of acid

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 ¹base 7a) 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

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acidy

\ˈa-sə-dē\ adjective

See acid defined for English-language learners

Examples of acid in a Sentence

the acids in your stomach
the kinds of acid found in your stomach

Recent Examples of acid from the Web

The smokiness from the mezcal, sweetness from the agave and acid from the lime and orange are expressed in a subtle manner making for an enjoyable sipping experience.

— lindsey mcclave, The Courier-Journal, "El Mundo's 'controlled chaos' is worth the delicious wait | Review," 30 Aug. 2017
The delivery driver was one of the latest victims in an alarming surge of acid attacks in Britain.

— karla adam, Washington Post, "As Britain cracks down on weapons, criminals turn to acid attacks," 26 Aug. 2017
Other alleged abuse included scalding two dogs with acid, burning their flesh.

— teri figueroa, sandiegouniontribune.com, "Victim details dogs' suffering at suspect's hearing," 23 Aug. 2017
When exposed to water, light, and carbon dioxide, the crystals on these bacteria make acetic acid—vinegar, basically.

— avery thompson, Popular Mechanics, "Cyborg Bacteria Could Turn CO2 Into Fuel," 22 Aug. 2017
Through genetic modification, the company lowered the amount of saturated fat in standard soybean oil by 20 percent and raised the omega-9 fatty acids to rival that of olive oil.

— deena shanker, Bloomberg.com, "Trans Fat Is (Almost) Out of Your Food. Here's What's Going In," 17 Aug. 2017
Because of zucchini's high water and fiber content, its consumption is considered by nutritionists as a great way to stay (healthily) full; the nutrient-dense fruit even contains omega-3 fatty acids.

— birmingham magazine, AL.com, "How to cook with summer's favorite squash," 10 Aug. 2017
Topical retinoids or products with salicylic acid or tar may also be used to help reduce the scale of the lesions.

— kate e. oberlin, m.d., and lawrence a. schachner, m.d. taking the next steps, miamiherald, "Your child has psoriasis, now how do you treat it?," 31 July 2017
Try using a concealer with a zit-zapping ingredient like salicylic acid.

— the editors, Marie Claire, "45 Expert-Approved Beauty Tips to Hack Your Makeup Routine," 14 July 2017

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'acid.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

Origin and Etymology of acid

see ²acid

NEW! Time Traveler

First Known Use: 1650

See Words from the same year

Other Chemical Engineering Terms

alkali, cation, decant, hygroscopic, isotope, oxidize, slurry, solute, viscous

acid

adjective ac·id \ ˈa-səd \

Definition of acid

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

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acidly

adverb

—

acidness

noun

See acid defined for English-language learners

See acid defined for kids

Examples of acid in a Sentence

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 of acid from the Web

Trees were healthier, not stressed by drought and killed by today’s massive insect infestations, acid rain, pollution and other causes.

— irene wanner, The Seattle Times, "Author covers what’s kindling the increase of megafires," 27 Aug. 2017
Bronze does not respond well to acid rain, urban pollution, and bird droppings, according to the gsa.gov website.

— howard gensler, Philly.com, "What are the options for a 2,000 pound Frank Rizzo statue?," 18 Aug. 2017
Acid attacks like the one Karli endured are extremely rare in the United States.

— savita iyer, Teen Vogue, "The Complex Task of Deterring Acid Attacks, Explained," 10 Aug. 2017
Between the searing 120+ degree temperatures, the constant volcanic eruptions, and the acid pools, life would have a tough time.

— avery thompson, Popular Mechanics, "Scientists Find Life In Earth's Most Barren Hellhole," 7 Aug. 2017
If whiteheads have already sprouted, a 2% salicylic acid spot treatment can pinpoint the spots in need of extra exfoliation.

— lauren hubbard, Harper's BAZAAR, "How to (Finally) Get Rid of Whiteheads," 4 Aug. 2017
Low to medium lactic acid character is evident in all examples as sharp, refreshing sourness (craftbeer.com) PAIRING OPTIONS •

— sam calagione, SI.com, "Summer Beer Guide: Step (and drink) out of your comfort zone this season," 18 July 2017
Some flowers are acid green, some maroon and some a deep crimson.

— the washington post, NOLA.com, "These stunning plants all have one thing in common: A taste for blood," 3 July 2017
An acid product is only as potent as the free-acid compounds floating around inside it.

— kara nesvig, Allure, "6 Things You Didn't Know About Acids," 24 June 2017

Origin and Etymology of acid

French or Latin; French acide, from Latin acidus, from acēre to be sour — more at acet-

NEW! Time Traveler

First Known Use: 1649

See Words from the same year

acid Synonyms

Synonyms

sour, acidic, acidulous, sourish, tart, tartish, vinegary

Antonyms

amiable, good-humored, good-natured, good-tempered

Related Words

dry, soured, unsweetened; pungent, sharp, tangy, zestful, zesty, zingy; astringent, puckery hyperacid

Near Antonyms

sweet; bland, smooth; flat, flavorless, insipid, savorless, tasteless, zestless; dilute, thin, watery, weak

Other Chemical Engineering Terms

alkali, cation, decant, hygroscopic, isotope, oxidize, slurry, solute, viscous

ACID Defined for English Language Learners

acid

adjective

Definition of acid for English Language Learners

: of, relating to, or having the qualities of an acid
: sharp, strong, and critical in tone

acid

noun

Definition of acid for English Language Learners

chemistry : a chemical with a sour taste that forms a salt when mixed with a base

ACID Defined for Kids

acid

adjective ac·id \ ˈa-səd \

Definition of acid for Students

1 :having a taste that is sour, bitter, or stinging

2 :harsh or critical in tone

acid remarks

3 :of, relating to, or like an acid

an acid solution

—

acidly

adverb

spoke acidly

acid

noun

Definition of acid for Students

:a chemical compound that tastes sour and forms a water solution which turns blue litmus paper red

Medical Dictionary

acid

adjective ac·id \ ˈas-əd \

medical Definition of acid

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

—not used technically

acid

noun

medical Definition of acid

1 :a sour substance; specifically :any of various typically water-soluble and sour compounds that in solution are capable of reacting with a base to form a salt, that redden litmus, that have a pH less than 7, and that are hydrogen-containing molecules or ions able to give up a proton to a base or are substances able to accept an unshared pair of electrons from a base

2 :lsd