acid /as″id/ [L, acidus, sour] , 1. a compound that yields hydrogen ions when dissociated in aqueous solution (Arrhenius definition), acts as a hydrogen ion donor (Brønsted definition), or acts as an electron pair acceptor (Lewis definition). Acids turn blue litmus red, have a sour taste, and react with bases to form salts. Acids have chemical properties essentially opposite to those of bases. See also alkali, base. 2. (Slang) LSD. 3. sour or bitter to the taste. −acidic, adj.
