sandworm

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Any of various marine burrowing annelid worms, such as a lugworm or clamworm, inhabiting coastal sand or mud and often used as fishing bait.

from The Century Dictionary.

• noun A worm that lives in the sand: applied to various arenicolous or limicolous annelids, found especially in the sand of the sea-shore, and quite different from ordinary earthworms. They are much used for bait.
• noun A worm that constructs a sand-tube, as a species of Sabellaria.

from the GNU version of the Collaborative International Dictionary of English.

• noun Any one of numerous species of annelids which burrow in the sand of the seashore.
• noun Any species of annelids of the genus Sabellaria. They construct firm tubes of agglutinated sand on rocks and shells, and are sometimes destructive to oysters.
• noun The chigoe, a species of flea.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun UK The lugworm.
• noun US The clam worm or ragworm.
• noun The chigoe, a species of flea.