Source : Webster's Revised Unabridged Dictionary (1913)

Tannin \Tan"nin\, n. [Cf. F. tannin.] (Chem.)
   Same as {Tannic acid}, under {Tannic}.

Source : WordNet®

tannin
     n : any of various complex phenolic substances of plant origin;
         used in tanning and in medicine [syn: {tannic acid}]