The Collaborative International Dictionary of English v.0.48:

Hippocrene \Hip"po*crene\, n. [L., fr. Gr. ?; "i`ppos horse + ?
   a fountain.]
   A fountain on Mount Helicon in B[oe]otia, fabled to have
   burst forth when the ground was struck by the hoof of
   Pegasus. Also, its waters, which were supposed to impart
   poetic inspiration. --Keats.
   [1913 Webster]

         Nor maddening draughts of Hippocrene.    --Longfellow.
   [1913 Webster]