Source : Webster's Revised Unabridged Dictionary (1913)

Prehnitic \Prehn*it"ic\, a. (Chem.)
   Pertaining to, or designating, a tetrabasic acid of benzene
   obtained as a white crystalline substance; -- probably so
   called from the resemblance of the wartlike crystals to the
   mammill[ae] on the surface of prehnite.