I. ac ‧ id 1 W3 /ˈæsəd, ˈæsɪd/ BrE AmE noun
1 . [uncountable and countable] a chemical substance that has a ↑ pH of less than 7. Strong acids can burn holes in material or damage your skin:
2 . [uncountable] informal the drug ↑ LSD
II. acid 2 BrE AmE adjective
[ Date: 1600-1700 ; Language: French ; Origin: acide , from Latin acidus , from acere 'to be sour' ]
1 . having a sharp sour taste SYN bitter :
a juicy apple with a slightly acid flavour
2 . acid remark/comment/tone etc an acid remark uses humour in an unkind way to criticize someone:
I was expecting another of his acid remarks, but he remained silent.
3 . the acid test a way of finding out whether something is as good as people say it is, whether it works, or whether it is true:
People ask if the team is good enough. This match will be the acid test.
4 . technical an acid soil does not contain much ↑ lime 1 (3):
Blueberry bushes need a very acid soil.
—acidity /əˈsɪdəti, əˈsɪdɪti/ noun [uncountable]