Acid (&unr_;), a. [L. acidus sour, fr. the root ak to be sharp: cf. F. acide. Cf. Acute.] 1. Sour, sharp, or biting to the taste; tart; having the taste of vinegar: as, acid fruits or liquors. Also fig.: Sour-tempered.
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He was stern and his face as acid as ever. A. Trollope.
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2. Of or pertaining to an acid; as, acid reaction.
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