The Collaborative International Dictionary of English v.0.48:

Gallotannic \Gal`lo*tan"nic\, a. [Gall nutgall + tannic.]
   (Chem.)
   Pertaining to the tannin or nutgalls.
   [1913 Webster]

   Gallotannic acid. See Tannic acid, under Tannic.
      [1913 Webster]