1
a
: 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
2
a
: 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
acidly
adverb
acidness
noun
Examples of acid in a Sentence
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
Chad De Guzman, Time, 1 June 2026
New York — In New York’s Hudson Valley, the artist Anicka Yi has erected columns bursting with mercurial microbial life, in hues of acid green and coffee, arranged like an archaeological dig at Storm King Art Center.
—Jacqui Palumbo, CNN Money, 29 May 2026
There are acid critiques of settler colonialism alongside tributes to the majesty of the American landscape, sober revisitations of enslavement alongside hopeful pleas for liberation, bitter denouncements of intervention in wars abroad alongside quaint homages to homespun Americanness.
—Alex Greenberger, ARTnews.com, 28 May 2026
Everyone has an acid tongue and brims with spiteful resentment.
—The Week Us, TheWeek, 27 May 2026
See All Example Sentences for acid
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Adjective
De la Espriella also represented some high-profile victims, including Natalia Ponce de León, who was the target of an acid attack in 2014, and Rosa Elvira Cely, whose murder in 2012 generated national outrage and led to the creation of Colombia’s femicide laws.
—Chad De Guzman, Time, 1 June 2026
New York — In New York’s Hudson Valley, the artist Anicka Yi has erected columns bursting with mercurial microbial life, in hues of acid green and coffee, arranged like an archaeological dig at Storm King Art Center.
—Jacqui Palumbo, CNN Money, 29 May 2026
There are acid critiques of settler colonialism alongside tributes to the majesty of the American landscape, sober revisitations of enslavement alongside hopeful pleas for liberation, bitter denouncements of intervention in wars abroad alongside quaint homages to homespun Americanness.
—Alex Greenberger, ARTnews.com, 28 May 2026
Everyone has an acid tongue and brims with spiteful resentment.
—The Week Us, TheWeek, 27 May 2026
See All Example Sentences for acid
Cite this Entry
“Acid.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/acid. Accessed 11 Jun. 2026.
Copy CitationKids Definition
acid
2 of 2 noun1
: a sour substance
2
: a compound that usually dissolves in water, has a sour taste, reacts with a base to form a salt, and turns litmus paper red
3
: lsd
Medical Definition
acid
1 of 2 noun1
: 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 sense 3a) 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
: lsd
acid
2 of 2 adjective
ac·id
ˈas-əd 
1
: sour, sharp, or biting to the taste
2
a
: 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
see also acid reflux
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