acid

Concise Oxford English Dictionary © 2008 Oxford University Press:
acid/ˈasɪd/

▶noun

• 1 a substance (typically, a corrosive or sour-tasting liquid) with particular chemical properties including turning litmus red, neutralizing alkalis, and dissolving some metals.

• 2 Chemistry any molecule able to donate a proton or accept electrons in reactions.

• 3 informal the drug LSD.

▶adjective

• 1 containing or having the properties of an acid; having a pH of less than 7.

• 2 sharp-tasting or sour.

• 3 (of remarks) bitter or cutting.

• 4 Geology & Metallurgy rich in silica.

– derivatives
acidification noun,
acidify verb (acidifies, acidifying, acidified),
acidly adverb,
acidy adjective.

– origin C17: from L. acidus, from acere ‘be sour’.