acid

noun

Updated on: 18 Apr 2018

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

—

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

My only reaction beyond local soreness was an acid stomach for a day or two.

— jane e. brody, New York Times, "Why You Should Get the New Shingles Vaccine," 9 Apr. 2018
This formula contains calcium carbonate, which can neutralize stomach acid.

— macaela mackenzie, Allure, "Here's What's Causing Your Indigestion Pain — and How to Get Rid of It," 3 Apr. 2018
The children who took folinic acid showed more improvement in verbal communication, as measured by standardized tests, than those who took the placebo.

— nicholette zeliadt, Washington Post, "Taking folic acid may lower the risk of autism and ease features of the condition," 2 Apr. 2018
Callaghan takes a razor dipped in acid to slash through the thickets of the impossible standards of appearance and behavior men impose upon women — and that women then impose on themselves and each other.

— kerry reid, chicagotribune.com, "In 'Women Laughing Alone with Salad,' a playwright hilariously slices and dices questions of sex, advertising and body image," 22 Mar. 2018
The turquoise sky, the confetti-speckled purple thunderclouds, the simmering red mountains on the horizon, the acid green grass, along with the stripes and polka dots worn by two Native American women, are all a party for the eyes.

— cate mcquaid, BostonGlobe.com, "At PEM, T.C. Cannon’s paintings exult and reproach," 21 Mar. 2018
Second, if possible, choose natural cocoa over Dutch processed cocoa, which is treated with an alkali, a compound that neutralizes acid.

— lisa drayer, CNN, "Is dark chocolate healthy?," 8 Mar. 2018
Acid Reflux Disease Also known as gastroesophageal reflux disease (GERD), this causes a painful burning sensation, or heartburn, in the lower chest when stomach acid rises back up into your esophagus.

— locke hughes, Redbook, "9 Ways Digestive Problems Could Be Totally Screwing With Your Weight," 17 Jan. 2018
Of course, most Republicans would rather eat cactus needles soaked in battery acid than push for national health care right now, so the new tax law instead tries to cripple the Affordable Care Act.

— kevin maney, Newsweek, "Trump Tax Code Will Lead to Fewer Full-Time Jobs and Fewer Homeowners," 10 Jan. 2018

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

borrowed from Medieval Latin acidum, going back to Latin, neuter of acidus 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

Tina Fey: Tony Nominee? Fans of all things fetch will be delighted by Fey's book, which preserves the blend of acid humor and poignancy in her script from the original 2004 movie.

— rebecca milzoff, Billboard, "5 Takeaways From Broadway's 'Mean Girls' Musical," 9 Apr. 2018
Sulfide deposits can release acidic material in water in a process known as acid mine drainage.

— lee bergquist, Milwaukee Journal Sentinel, "New group that's challenging existing environmental groups on mining in Wisconsin has Republican ties," 2 Apr. 2018
Do not apply wood ash to acid-loving plants such as blueberries, rhododendrons and azaleas.

— kym pokorny, OregonLive.com, "Sweep wood ash from the fireplace to the garden," 20 Mar. 2018
The lawsuit says Idlewild administrators failed to handle her son’s acid reflux, esophagitis and food allergies properly.

— ann doss helms, charlotteobserver, "Class volunteers get sued by a fellow parent. Why CMS says the district can’t help. | Charlotte Observer," 30 Mar. 2018
Michelle Dewey, his partner, suspected acid reflux, not the stage IV pancreatic cancer that he’s been treated for ever since.

— cassie owens, Philly.com, "Philly Zine Fest founder maintains successful GoFundMe page for his cancer bills, and it still isn't enough," 20 Mar. 2018
These accidental bactericides included proton-pump inhibitors such as omeprazole (used to treat acid reflux), calcium-channel blockers (to lower blood pressure), antihistamines, painkillers and antipsychotics.

— The Economist, "Non-antibiotic drugs promote antibiotic resistance," 19 Mar. 2018
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
For the new design, researchers led by chemist Jing Gu of San Diego State University added coatings to the semiconductor layers to prevent acid corrosion.

— melissa c. lott, Scientific American, "This Advance Brings Us a Lot Closer to a "Hydrogen Economy"," 1 May 2017

Origin and Etymology of acid

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

NEW! Time Traveler

First Known Use: 1649

See Words from the same year

acid Synonyms

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