Source : Webster's Revised Unabridged Dictionary (1913)

Shipworm \Ship"worm`\, n. (Zo["o]l.)
   Any long, slender, worm-shaped bivalve mollusk of {Teredo}
   and allied genera. The shipworms burrow in wood, and are
   destructive to wooden ships, piles of wharves, etc. See
   {Teredo}.

Source : WordNet®

shipworm
     n : wormlike marine bivalve that bores into wooden piers and
         ships by means of drill-like shells [syn: {teredinid}]