Source : Webster's Revised Unabridged Dictionary (1913)

Dripstone \Drip"stone`\, n. (Arch.)
   A drip, when made of stone. See {Drip}, 2.

Source : WordNet®

dripstone
     n 1: the form of calcium carbonate found in stalactites and
          stalagmites
     2: a protective drip that is made of stone [syn: {hoodmold}, {hoodmould}]