/ ˈæsɪd; NAmE / noun , adjective
■ noun
1.
[ U , C ] ( chemistry ) a chemical, usually a liquid, that contains hydrogen and has a pH of less than seven. The hydrogen can be replaced by a metal to form a salt. Acids are usually sour and can often burn holes in or damage things they touch.
—compare alkali
—see also acetic acid , amino acid , ascorbic acid , citric acid , hydrochloric acid , lactic acid , nitric acid , nucleic acid , sulphuric acid
2.
[ U ] ( slang ) = LSD
■ adjective
1.
( technical ) that contains acid or has the essential characteristics of an acid; that has a pH of less than seven :
Rye is tolerant of poor, acid soils.
—compare alkaline
2.
that has a bitter sharp taste
SYN sour :
acid fruit
➡ note at bitter
3.
( of a person's remarks ) critical and unkind
SYN sarcastic , cutting :
an acid wit
••
WORD ORIGIN
early 17th cent. (in the sense sour-tasting ): from Latin acidus , from acere be sour.