Source : Webster's Revised Unabridged Dictionary (1913)

Alkahest \Al"ka*hest\, n. [LL. alchahest, F. alcahest, a word
   that has an Arabic appearance, but was probably arbitrarily
   formed by Paracelsus.]
   The fabled ``universal solvent'' of the alchemists; a
   menstruum capable of dissolving all bodies. --
   {Al`ka*hes"tic}, a.

Source : WordNet®

alkahest
     n : hypothetical universal solvent once sought by alchemists
         [syn: {alcahest}, {universal solvent}]