In technical terms, acid is a substance that can react with a base to make a salt. In practical terms, acid is the stuff you want to keep off your hands, or any part of you, because it will eat away your skin.

Not all acids will eat skin away. The citric acid in oranges and other citrus fruits gives them their tasty tang. There is a hallucinogenic street drug called acid that eats away at the user’s sense of reality. Words sometimes have the qualities of acid. In acidic speech, words feel corrosive to the listener’s sensibilities. This one’s perhaps the most frequent and most destructive of all.

Primary Meanings of acid

any of various water-soluble compounds having a sour taste and capable of turning litmus red and reacting with a base to form a salt
having the characteristics of an acid
street name for lysergic acid diethylamide
Full Definitions of acid

n any of various water-soluble compounds having a sour taste and capable of turning litmus red and reacting with a base to form a salt

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alcapton, alkapton, homogentisic acid
an acid formed as an intermediate product of the metabolism of tyrosine and phenylalanine
arsenic acid
an acid formed from arsenic pentoxide
cerotic acid, hexacosanoic acid
a white solid fatty acid found in waxes (such as beeswax)
chloric acid
(HClO3) a strong unstable acid with an acrid odor found in chlorate salts
chlorous acid
(HClO2) a strongly oxidizing acid; known only in solution
monobasic acid
an acid containing only one replaceable hydrogen atom per molecule
dibasic acid
an acid containing two replaceable hydrogen atoms per molecule
tribasic acid
an acid containing three replaceable hydrogen atoms per molecule
tetrabasic acid
an acid containing four replaceable hydrogen atoms per molecule
fulminic acid
(CNOH) an unstable acid occurring mainly in the form of explosive salts and esters that is isomeric with cyanic acid
gamma acid
a crystalline acid used to make azo dyes
hydriodic acid
(HI) a colorless or yellow aqueous solution of hydrogen iodide
hydrocyanic acid, prussic acid
a solution of hydrogen cyanide in water; weak solutions are used in fumigating and in the synthesis of organic compounds
hydroxy acid
any acid that has hydroxyl groups in addition to the hydroxyl group in the acid itself
hyponitrous acid
an explosive white crystalline weak acid (H2N2O2)
lysergic acid
a crystalline acid often used in medical research; obtained from ergotic alkaloids
manganic acid
a dibasic acid (H2MnO4) found only in solution and in manganate salts
2-methylpropenoic acid, methacrylic acid
an unsaturated acid (C4H6O2) used to make resins and plastics
selenic acid
a strong acid (H2SeO4) analogous to sulfuric acid
sulfonic acid, sulphonic acid
an acid derived from sulphuric acid
titanic acid
a white weak acid that is a hydrated form of titanium dioxide
perchloric acid
a powerful oxidizing agent; forms perchlorates
carboxylic acid
an organic acid characterized by one or more carboxyl groups
aminobenzoic acid
a derivative of benzoic acid
aqua fortis, nitric acid
acid used especially in the production of fertilizers and explosives and rocket fuels
nitrous acid
an unstable inorganic acid known only in solution and as nitrite salts
aqua regia, nitrohydrochloric acid
a yellow fuming corrosive mixture of nitric and hydrochloric acid that dissolves metals (including gold)
barbituric acid, malonylurea
a white crystalline acid derived from pyrimidine; used in preparing barbiturate drugs
Prevacid, lansoprazole
antacid (trade name Prevacid) that suppresses acid secretion in the stomach
boracic acid, boric acid
any of various acids containing boron and oxygen
boric acid, orthoboric acid
a white or colorless slightly acid solid that is soluble in water and ethanol; used in the manufacture of glass and paper and adhesives and in detergents and as a flux in welding; also used as an antiseptic and food preservative
bromic acid
an unstable acid used as an oxidizing agent
carbamic acid
an acid that is known only by virtue of its salts (as ammonium carbamate) or its esters (as urethane)
carbolic acid, hydroxybenzene, oxybenzene, phenol, phenylic acid
a toxic white soluble crystalline acidic derivative of benzene; used in manufacturing and as a disinfectant and antiseptic; poisonous if taken internally
carbonic acid
a weak acid known only in solution; formed when carbon dioxide combines with water
chromic acid
an unstable acid known only in solution and as chromate salts
citric acid
a weak water-soluble acid found in many fruits (especially citrus fruits); used as a flavoring agent
cyanamid, cyanamide
a weak soluble dibasic acid (the parent acid of cyanamide salts)
cyanic acid
a colorless poisonous volatile liquid acid that hydrolyzes readily to ammonia and carbon dioxide
cyanuric acid
a trimer of cyanic acid
ferricyanic acid
a brown unstable acid formed from ferricyanide
ferrocyanic acid
a white unstable acid formed from ferrocyanide salts
fluoroboric acid
an acid of fluorine and boron
fluosilicic acid, hydrofluosilicic acid
an unstable poisonous corrosive acid known primarily in the form of its salts
formic acid
a colorless pungent fuming vesicatory liquid acid HCOOH found naturally in ants and many plants or made catalytically from carbon monoxide and steam; used in finishing textiles and paper and in the manufacture of insecticides and fumigants
fumaric acid
a colorless crystalline acid with a fruity taste; used in making polyester resins
gallic acid
a colorless crystalline acid obtained from tannin
glyceric acid
a syrupy acid obtained by oxidation of glycerol or glyceraldehyde
glycolic acid, glycollic acid, hydroxyacetic acid
a translucent crystalline compound found in sugar cane and sugar beets and unripe grapes
hydrobromic acid
an aqueous solution of hydrogen bromide that is a strong liquid acid
chlorohydric acid, hydrochloric acid
an aqueous solution of hydrogen chloride; a strongly corrosive acid
hydrogen chloride
a colorless corrosive gas (HCl)
hydrofluoric acid
a weak poisonous liquid acid; formed by solution of hydrogen fluoride in water
hydroiodic acid
an acid formed by aqueous solution of hydrogen iodide
hypochlorous acid
a weak unstable acid known only in solution and in its salts; used as a bleaching agent and as an oxidizing agent
iodic acid
a soluble crystalline acid; used as a reagent and disinfectant
isocyanic acid
an acid known only in the form of its esters
itaconic acid
a crystalline carboxylic acid; occurs in some fermentations of sugars
maleic acid
a colorless crystalline compound found in unripe fruit (such as apples or tomatoes or cherries) and used mainly to make polyester resins
oxalacetic acid, oxaloacetic acid
an acid formed by oxidation of maleic acid (as in metabolism of fats and carbohydrates)
ethanedioic acid, oxalic acid
a toxic colorless crystalline organic acid found in oxalis and other plants; used as a bleach and rust remover and in chemical analysis
oxyacid, oxygen acid
any acid that contains oxygen
pantothen, pantothenic acid
a vitamin of the vitamin B complex that performs an important role in the oxidation of fats and carbohydrates and certain amino acids; occurs in many foods
PABA, para aminobenzoic acid
a metabolic acid found in yeast and liver cells; used to make dyes and drugs and sun blockers
pectic acid
a complex acid that occurs in ripe fruit and some vegetables
permanganic acid
an unstable purple acid (HMnO4) known only in solution or of permanganate salts
phthalic acid
a colorless acid used to make dyes and perfumes
picric acid
a yellow toxic highly explosive strong acid; used in high explosives and as a dye and in chemical reactions
pyruvic acid
a colorless acid formed as an important intermediate in metabolism or fermentation
dichromic acid
the hypothetical acid (H2Cr2O7) from which dichromates are derived; known only in solution and in the form of dichromate salts
silicic acid
a jellylike substance (hydrated silica)
sulfanilic acid, sulphanilic acid
a crystalline acid made from aniline and used as a dye
thiocyanic acid
an unstable acid that can be obtained by distilling a thiocyanate salt
toluic acid
an isomeric acid derived from toluene
triphosphoric acid
an acid that is a partial anhydride of three molecules of phosphoric acid; known chiefly in the form of its salts and esters
undecylenic acid
an acid that is a component of perspiration
uric acid
a white tasteless odorless crystalline product of protein metabolism; found in the blood and urine
oil of vitriol, sulfuric acid, sulphuric acid, vitriol
(H2SO4) a highly corrosive acid made from sulfur dioxide; widely used in the chemical industry
xanthic acid
any of a class of unstable organic acids containing sulphur
acetic acid, ethanoic acid
a colorless pungent liquid widely used in manufacturing plastics and pharmaceuticals
adipic acid, hexanedioic acid
a carboxylic acid used in the manufacture of nylon
hydroxybenzoic acid
a crystalline derivative of benzoic acid
hypophosphoric acid
a crystalline tetrabasic acid (H4P2O6)
hypophosphorous acid, orthophosphorous acid, phosphorous acid
a clear or yellow monobasic acid (H3PO2)
juniperic acid
a crystalline acid found in the exudations of some conifers
polyphosphoric acid
a series of oxyacids of phosphorus
mucic acid
a solid acid (C6H10O8) found in milk or sugar
octanedioic acid, suberic acid
a dicarboxylic acid found in cork
succinic acid
a dicarboxylic acid (C4H6O4) active in metabolic processes
saccharic acid
a white dicarboxylic acid formed from oxidation of sugar or starch
decanedioic acid, sebacic acid
a dicarboxylic acid used to make resins
sorbic acid
a white crystalline carboxylic acid used as a preservative
pentanoic acid, valeric acid
a clear liquid carboxylic acid used in perfumes and drugs
fatty acid
any of a class of aliphatic monocarboxylic acids that form part of a lipid molecule and can be derived from fat by hydrolysis; fatty acids are simple molecules built around a series of carbon atoms linked together in a chain of 12 to 22 carbon atoms
battery acid, electrolyte acid
dilute sulfuric acid used in storage batteries
benzoic acid
a white crystalline solid occurring in many resins
propanoic acid, propionic acid
a liquid fatty acid found in milk and sweat and in fuel distillates
lactic acid
a clear odorless hygroscopic syrupy carboxylic acid found in sour milk and in many fruits
muriatic acid
a former name for hydrochloric acid
periodic acid
any acid of iodine that contains oxygen
perboric acid
a form of boric acid
orthophosphoric acid, phosphoric acid
an acid used in fertilizers and soaps: H3PO4
acrylic acid, propenoic acid
an unsaturated liquid carboxylic acid used in the manufacture of acrylic resins
2-hydroxybenzoic acid, salicylic acid
a white crystalline substance with a bitter aftertaste; used as a fungicide or in making aspirin or dyes or perfumes
tartaric acid
an acid found in many fruits; used in soft drinks and confectionery and baking powder
tungstic acid
an oxyacid of tungsten (often polymeric in nature) formed by neutralizing alkaline tungstate solutions
vanadic acid, vanadium pentoxide
any of various oxyacids of vanadium; known mostly in the form of its salts
Type of:
chemical compound, compound
(chemistry) a substance formed by chemical union of two or more elements or ingredients in definite proportion by weight

adj having the characteristics of an acid

“an acid reaction”
being or containing an acid; of a solution having an excess of hydrogen atoms (having a pH of less than 7)

adj being sour to the taste

acidic, acidulent, acidulous
having a sharp biting taste

adj harsh or corrosive in tone

“a barrage of acid comments”
acerb, acerbic, acrid, bitter, blistering, caustic, sulfurous, sulphurous, virulent, vitriolic
disagreeable to the senses, to the mind, or feelings

n street name for lysergic acid diethylamide

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