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
adjectiveDefinition 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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Merriam-Webster unabridged
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Time Traveler for acid
The first known use of acid was in 1649
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