acid

[as-id]

noun

1. Chemistry.,  a compound usually having a sour taste and capable of neutralizing alkalis and reddening blue litmus paper, containing hydrogen that can be replaced by a metal or an electropositive group to form a salt, or containing an atom that can accept a pair of electrons from a base. Acids are proton donors that yield hydronium ions in water solution, or electron-pair acceptors that combine with electron-pair donors or bases.

2. a substance with a sour taste.

3. something, as a remark or piece of writing, that is sharp, sour, or ill-natured.

   His criticism was pure acid.

4. Slang.,  LSD.

adjective

1. Chemistry.

   1. belonging or pertaining to acids or the anhydrides of acids.

   2. having only a part of the hydrogen of an acid replaced by a metal or its equivalent.

      an acid phosphate.

   3. having a pH value of less than 7.

2. sharp or biting to the taste; tasting like vinegar; sour.

   acid fruits.

3. sharp, biting, or ill-natured in mood, manner, etc..

   an acid remark; an acid wit.

   Synonyms: tart, vitriolic, biting, acerbic

4. Geology.,  containing much silica.

5. Metallurgy.,  noting, pertaining to, or made by a process in which the lining of the furnace, or the slag that is present, functions as an acid in high-temperature reactions in taking electrons from oxide ions: usually a siliceous material, as sand or ganister.

acid

/ ˈæsɪd /

noun

1. any substance that dissociates in water to yield a sour corrosive solution containing hydrogen ions, having a pH of less than 7, and turning litmus red See also Lewis acid

2. a sour-tasting substance

3. a slang name for LSD

adjective

1. chem

   1. of, derived from, or containing acid

      an acid radical

   2. being or having the properties of an acid

      sodium bicarbonate is an acid salt

2. sharp or sour in taste

3. cutting, sharp, or hurtful in speech, manner, etc; vitriolic; caustic

4. (of rain, snow, etc) containing pollutant acids in solution

5. (of igneous rocks) having a silica content of more than 60% of the total and containing at least one tenth quartz

6. metallurgy of or made by a process in which the furnace or converter is lined with an acid material

   acid steel

acid

1. Any of a class of compounds that form hydrogen ions when dissolved in water, and whose aqueous solutions react with bases and certain metals to form salts. Acids turn blue litmus paper red and have a pH of less than 7. Their aqueous solutions have a sour taste.

2. Compare base

acid

1. A sour-tasting material (usually in a solution) that dissolves metals and other materials. Technically, a material that produces positive ions in solution. An acid is the opposite of a base and has a pH of 0 to 7. A given amount of an acid added to the same amount of a base neutralizes the base, producing water and a salt. Common vinegar, for example, is a weak solution of acetic acid.

Figuratively, acid applies to anything sour or biting; for example, an “acid wit” is sharp and unpleasant.

Other Word Forms

• acidly adverb
• acidness noun
• nonacid noun
• preacid adjective
• preacidness noun
• semiacid adjective
• acidy adjective

Word History and Origins

Origin of acid¹

First recorded in 1620–30; from Latin acidus “sour,” akin to ācer “sharp,” acētum “vinegar”; acescent, acicula

Word History and Origins

Origin of acid¹

C17: (first used by Francis Bacon): from French acide or Latin acidus, from acēre to be sour or sharp

Idioms and Phrases

Idioms

1. put on the acid, to importune someone, as for money, sexual favors, or confidential information.

Synonym Study

Acid, astringent are terms used figuratively of wit or humor. Acid suggests a sharp, biting, or ill-natured quality: an acid joke about an opponent. Astringent connotes severity but usually also a bracing quality, as of something applied with curative intent: astringent criticism.

Example Sentences

They found that a small variation in the protein's amino acid sequence serves as a "tag," instructing the cell on whether to keep the protein or send it out.

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A new study has found that the benefits of a fatty acid known as eicosapentaenoic acid vary widely from person to person.

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The results indicate that both palmitic acid and stearic acid-rich interesterified fats, when consumed in normal dietary amounts, do not appear to raise short-term risk factors linked to heart disease.

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Some vitamins, such as folic acid, can discolor urine and lead to inaccurate results.

Read more on The Wall Street Journal

One group received no treatment, the second completed a 30-day swimming routine, and the third both swam and received omega-3 supplements, a fatty acid known for reducing inflammation in chronic diseases.

Read more on Science Daily

Related Words

• acerbic 
• biting 
• caustic 
• mordant 
• nasty 
• sarcastic 
• stinging www.thesaurus.com
• trenchant 
• vitriolic 

When To Use

What does acid mean?

In science, an acid is a sour-tasting substance that releases hydrogen ions when added to water. Acids will turn litmus to a red color and have a pH lower than 7.An acid is any substance that will release hydrogen ions when mixed with water. The amount of hydrogen ions that a substance releases is measured on the pH scale, which ranges from 0 to 14. The lower the pH number is, the more hydrogen ions that are being released. Water has a pH of 7, which is neutral on the pH scale. All acids have a pH lower than 7. A pH greater than 7 indicates an alkali, or base.Acids also have a sour taste, such as the acid found in lemons. A final quality that all acids share is that when they come into contact with litmus paper, they will turn the paper red.Acids are all around us and are used for a wide variety of purposes. Some common acids you can find in your house include lactic acid (in milk), ascorbic acid (in citrus fruits), and acetic acid (in vinegar).