acid

noun

\ ˈa-səd

Definition of acid

(Entry 1 of 2)

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

acid

adjective

Definition of acid (Entry 2 of 2)

1a : 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

2a : 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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Synonyms for acid

Synonyms: Adjective

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: Noun Whites threw nails to the bottom of pools in Cincinnati and poured bleach and acid in pools in St. Augustine, Florida. — Andre Toran, USA TODAY, "Unwelcome waters: Segregated public pools and the lasting effect they have on the Black community," 24 Feb. 2021 Each is named for the type of material they’re made with: Hyaluronic acid is naturally produced by your body and already found in your skin and cartilage. — Annie Tomlin, SELF, "10 Things to Know Before Trying Dermal Fillers," 25 Dec. 2020 Hyaluronic acid and moisturizing glycerin are the stars of this buildable coverage show. — Akili King, Vogue, "15 of the Best Foundations for Dry Skin to Try This Winter," 9 Dec. 2020 Hyaluronic acid helps add and lock in moisture, contributing to its impressive hydration scores in our Lab test. — Danusia Wnek, Good Housekeeping, "21 Best Hand Creams to Save Your Dry, Cracked Skin," 26 Oct. 2020 Trump’s physician, Dr. Sean Conley, said Friday doctors were providing Trump with an experimental antibody cocktail; vitamin D; famotidine, which is typically used to treat heartburn and acid reflux; the sleep aid melatonin; and an aspirin. — Ellen Knickmeyer, chicagotribune.com, "What we know — and what we don’t — about Trump’s COVID-19 diagnosis and treatment," 2 Oct. 2020 Colors were eye-popping, either prime or acid and the silhouette was tight and sporty, or flowing and diaphanous. — Thomas Adamson, Star Tribune, "Kenzo gets the buzz at bee-themed Paris Fashion Week show," 30 Sep. 2020 Pills and edibles, on the other hand, need to be carefully engineered so that they don’t get neutralized by stomach acid. — Purbita Saha, Popular Science, "Can CBD help you chill? Here’s what we know so far.," 4 Jan. 2021 The Retch, for example, combines the acid-spitting properties of L4D's Spitter and the hazardous-goo-splosion issues of L4D's Boomer. — Sam Machkovech, Ars Technica, "Back 4 Blood alpha test: Building decks, killing zombies, having co-op fun," 18 Dec. 2020 Recent Examples on the Web: Adjective The series might have climbed from the brain of a woke English grad student on an acid trip. — Katy Waldman, The New Yorker, "Alena Smith’s Subversive “Dickinson”," 25 Feb. 2021 These pillows are typically used to help alleviate symptoms of acid reflux, gastroesophageal reflux disease (GERD), and obstructive sleep apnea. — Jamie Kim, Good Housekeeping, "Every Type of Pillow You Need to Know About," 18 Feb. 2021 Ancestry is stuff a hero might inherit from biological parents, like walking speed, lifespan, and acid breath. — Cecilia D'anastasio, Wired, "D&D Must Grapple With the Racism in Fantasy," 24 Jan. 2021 Chen eventually pulled the narrow but varied palette from pieces like the painting in the primary bedroom, which atypically combines sunset pinks and purples with an acid green. — Alexandra Lange, ELLE Decor, "How One Architect Kept the Cozy in a Sleek Redo on Manhattan’s Upper East Side," 5 Jan. 2021 The million gallon tank collected 395,000 gallons of acid mine water that was neutralized once electricity was restored to the treatment facility a few days after the fire. — NBC News, "Wildfires fueled by climate change threaten toxic Superfund sites," 23 Dec. 2020 In the slightly alkaline soils common on the south shore, plants that prefer an acid soil condition may have difficulty obtaining iron. — Dan Gill, NOLA.com, "Even on evergreens, it's natural for leaves to yellow and drop. Here's how to tell if it's a problerm," 27 Jan. 2021 Stone’s psychedelic influences warp his band’s funk sound into something that feels like an acid trip. — Troy L. Smith, cleveland, "50 greatest Rock & Roll Hall of Fame albums of 1971," 22 Jan. 2021 Blazes at such sites could release toxins ranging from acid mine drainage to radioactive smoke. — NBC News, "Wildfires fueled by climate change threaten toxic Superfund sites," 23 Dec. 2020

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.

History and Etymology for acid

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

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Last Updated

1 Mar 2021

Cite this Entry

“Acid.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/acid. Accessed 3 Mar. 2021.

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More Definitions for acid

acid

noun

English Language Learners Definition of acid

(Entry 1 of 2)

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

acid

adjective

English Language Learners Definition of acid (Entry 2 of 2)

: of, relating to, or having the qualities of an acid

: sharp, strong, and critical in tone

See the full definition for acid in the English Language Learners Dictionary

acid

adjective

ac·id | \ ˈa-səd

Kids Definition of acid

(Entry 1 of 2)

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

acid

noun

Kids Definition of acid (Entry 2 of 2)

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

acid

adjective

ac·id | \ ˈas-əd

Medical Definition of acid

(Entry 1 of 2)

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 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 (Entry 2 of 2)

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

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