The Collaborative International Dictionary of English v.0.48:
Dripstone \Drip"stone`\, n. (Arch.) A drip, when made of stone. See Drip, 2. [1913 Webster]WordNet (r) 3.0 (2006):
dripstone n 1: the form of calcium carbonate found in stalactites and stalagmites 2: a protective drip that is made of stone [syn: dripstone, hoodmold, hoodmould]