adj 1  :  sour, sharp, or biting to the taste  2 a  :  of, relating to, or being an acid : also  :  having the reactions or characteristics of an acid <an solution>   b  of salts and esters  :  derived by partial exchange of replaceable hydrogen < sodium carbonate NaHCO₃>   c  :  marked by or resulting from an abnormally high concentration of acid < indigestion>  - not used technically
n 1  :  a sour substance : specif  :  any of various typically water-soluble and sour compounds that in solution are capable of reacting with a base to form a salt, that redden litmus, that have a pH less than 7, and that are hydrogen-containing molecules or ions able to give up a proton to a base or are substances able to accept an unshared pair of electrons from a base  2  :  LSD .
 
 
 
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