The Collaborative International Dictionary of English v.0.48:
Teredo \Te*re"do\, n.; pl. E. Teredos, L. Teredines. [L., a
worm that gnaws wood, clothes, etc.; akin to Gr. ?, L. terere
to rub.] (Zool.)
A genus of long, slender, wormlike bivalve mollusks which
bore into submerged wood, such as the piles of wharves,
bottoms of ships, etc.; -- called also shipworm. See
Shipworm. See Illust. in Appendix.