WordWeb Online

1. Being sour to the taste
   "They found a medium-sized red glossy fruit with a juicy and very acidic pulp";
   - acid, acidulent, acidulous
    
2. (chemistry) being or containing an acid; of a solution having an excess of hydrogen atoms (having a pH of less than 7)
    
3. (geology) containing a high percentage of silica

See also: acid, acid-forming, sour

Antonym: alkaline, amphoteric

Encyclopedia: Acidic