stalactite(n = noun.object) - a cylinder of calcium carbonate hanging from the roof of a limestone cave;
is a kind of cylinder
is a part of cave

   A pendent cone or cylinder of calcium carbonate resembling an icicle in form and mode of attachment. Stalactites are found depending from the roof or sides of caverns, and are produced by deposition from waters which have percolated through, and partially dissolved, the overlying limestone rocks. [1913 Webster]

stalactite, n. a deposit of calcium carbonate having the shape of a large icicle, formed by the trickling of water from the roof of a cave, cliff overhang, etc.

Derivative:
stalactic adj. stalactiform adj. stalactitic adj.

Etymology:
mod.L stalactites f. Gk stalaktos dripping f. stalasso drip

N  lining, inner coating, coating, stalactite, stalagmite, filling, stuffing, wadding, padding, wainscot, parietes, wall, lined.