\Tan"nic\, a.
Of or pertaining to tan; derived from, or resembling, tan;
as, tannic acid.
{Tannic acid}. (Chem.)
(a) An acid obtained from nutgalls as a yellow amorphous
    substance, {C14H10O9}, having an astringent taste, and
    forming with ferric salts a bluish-black compound, which
    is the basis of common ink. Called also {tannin}, and
    {gallotannic acid}.
(b) By extension, any one of a series of astringent
    substances resembling tannin proper, widely diffused
    through the vegetable kingdom, as in oak bark, willow,
    catechu, tea, coffee, etc.