any of a family (Teredinidae) of marine, bivalve mollusks with wormlike bodies: they burrow into and damage submerged wood, as of ships, pilings, etc.
See shipworm in American Heritage Dictionary 4
noun
Any of various wormlike marine mollusks of the genera Teredo and Bankia, having rudimentary bivalve shells with which they bore into wood, especially the submerged timbers of ships and wharves, often doing extensive damage.