(n.)
One of a class of compounds, generally but not always distinguished by their sour taste, solubility in water, and reddening of vegetable blue or violet colors. They are also characterized by the power of destroying the distinctive properties of alkalies or bases, combining with them to form salts, at the same time losing their own peculiar properties. They all contain hydrogen, united with a more negative element or radical, either alone, or more generally with oxygen, and take their names from this negative element or radical. Those which contain no oxygen are sometimes called hydracids in distinction from the others which are called oxygen acids or oxacids.
(n.)
A sour substance.
(a.)
Sour, sharp, or biting to the taste; tart; having the taste of vinegar: as, acid fruits or liquors. Also fig.: Sour-tempered.
(a.)
Of or pertaining to an acid; as, acid reaction.
Noun
1. 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
(hypernym) compound, chemical compound
(hyponym) alkapton, alcapton, homogentisic acid
(derivation) sour, acidify, acidulate, acetify
2. street name for lysergic acid diethylamide
(synonym) back breaker, battery-acid, dose, dot, Elvis, loony toons, Lucy in the sky with diamonds, pane, superman, window pane, Zen
(hypernym) lysergic acid diethylamide, LSD
Adjective
1. harsh or corrosive in tone; "an acerbic tone piercing otherwise flowery prose"; "a barrage of acid comments"; "her acrid remarks make her many enemies"; "bitter words"; "blistering criticism"; "caustic jokes about political assassination, talk-show hosts and medical ethics"; "a sulfurous denunciation"
(synonym) acerb, acerbic, acrid, bitter, blistering, caustic, sulfurous, sulphurous, venomous, virulent, vitriolic
(similar) unpleasant
2. containing acid; "an acid taste"
(similar) acidic
(classification) chemistry, chemical science
Meaning
A sure test, giving an incontestable result.
Origin
From Gold Rush days in the USA. Gold doesn't react to most acids as other metals do, but does react to nitric acid. To confirm that a find was gold they used this acid in 'the acid test'.
ref: Brewer's Dictionary of Phrase and Fable, 15th edition
adj., aigéadach, searbh
n.,aigéad, searbh