The Collaborative International Dictionary of English v.0.48:

Acetic \A*ce"tic\ (#; 277), a. [L. acetum vinegar, fr. acere to
   be sour.] (Chem.)
   (a) Of a pertaining to vinegar; producing vinegar; producing
       vinegar; as, acetic fermentation.
   (b) Pertaining to, containing, or derived from, acetyl, as
       acetic ether, acetic acid. The latter is the acid to
       which the sour taste of vinegar is due.
       [1913 Webster]