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

acidy

\ˈa-sə-dē\ adjective

See acid defined for English-language learners

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

Mint leaves, a natural source of salicylic acid, also help delicately slough off dull skin without damaging healing skin.

— emily watson, Philly.com, "Summer skin from the inside out," 13 July 2017
In a large pot over medium-high heat, add milk and citric acid/water mixture.

— nancy miller, The Courier-Journal, "It may be fast-casual food, but Red Herring's menu 'isn't a joke'," 11 July 2017
The body moisturizer is packed with safflower oil, aloe and essential fatty acids, and left our upper arms moisturized for hours without any sticky feeling.

— rachel nussbaum, Glamour, "Everything From This New Lifestyle Brand Is $3—and It's Legit," 11 July 2017
Look for a formula that contains l-ascorbic acid, one of the most effective forms of vitamin C. We like Paula's Choice Resist C15 Super Booster ($49; paulaschoice.com).

— lauren balsamo, Redbook, "How Long Does It Take Your Favorite Beauty Products to Work?," 10 July 2017
All of the variant Creutzfeldt-Jakob patients who were genetically tested had a similar amino acid structure for the normal prion protein in their bodies.

— mark johnson, Milwaukee Journal Sentinel, "In tracking a lethal family of diseases that threatens humans and animals, scientists have become the hunters," 6 July 2017
Her little brother was also splashed with acid and spent a day in the hospital with minor burns.

— CBS News, ""It melted my clothes off": Teen survives acid attack in Texas," 30 June 2017
The prohibition was ignored to ill effect on Aug. 11, 2003, when two workers at PF-4 inhaled plutonium after a sudden reaction between that material, organic cheesecloth, and acid.

— r. jeffrey smith, Science | AAAS, "Safety problems at a Los Alamos laboratory," 30 June 2017
White vinegar typically has more acid (between 5 percent and 8 percent), is more sour and generally is more effective in cleaning.

— hints from heloise, star-telegram.com, "Dog owner shares important pet-sitter tip," 29 June 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

play

adjective ac·id \ˈa-səd\

Definition of acid

1a : sour, sharp, or biting to the taste an acid flavorb : sharp, biting, or sour in manner, disposition, or nature an acid individual an acid personalityc : sharply clear, discerning, or pointed an acid wit acid criticismd : piercingly intense and often jarring acid yellow
2a : of, relating to, or being an acid; also : having the reactions or characteristics of an acid acid soil an acid solutionb of salts and esters : derived by partial exchange of replaceable hydrogen acid sodium carbonate NaHCO₃c : containing or involving the use of an acid (as in manufacture) an acid bathd : 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

See acid defined for English-language learners

See acid defined for kids

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

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
But after its second run in the lake, one of those periodic eruptions doused it in acid water.

— sarah zhang, The Atlantic, "The Tough Little Drone Ship That Explores Acid Lakes," 7 June 2017
One is similar in spelling to Solax (a muscle relaxer) or Solox (for acid reflux).

— doug ferguson, The Seattle Times, "Criminal expert: Tiger Woods made mistake issuing statement," 31 May 2017
One is similar in spelling to Solax (a muscle relaxer) or Solox (for acid reflux).

— doug ferguson, The Denver Post, "Tiger Woods made mistake issuing statement, per criminal expert," 31 May 2017
One is similar in spelling to Solax (a muscle relaxer) or Solox (for acid reflux).

— Bloomberg.com, "Woods Found Asleep at the Wheel, No Alcohol in His System," 30 May 2017
One is similar in spelling to Solax (a muscle relaxer) or Solox (for acid reflux).

— doug ferguson, courant.com, "Police: Tiger Woods Asleep On Roadside; No Alcohol In System," 30 May 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

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

play

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

play

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

play

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

play

adjective ac·id \ˈas-əd\

Medical Definition of acid

1: sour, sharp, or biting to the taste
2a: of, relating to, or being an acid; also : having the reactions or characteristics of an acid an acid solutionbof salts and esters : derived by partial exchange of replaceable hydrogen acid sodium carbonate NaHCO₃c: 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