The woodworm is found in some medieval encyclopedias. It is a worm that eats wood by grinding into it. It is generated when trees are cut down at the wrong time.

There is considerable confusion about what medieval and earlier writers called this worm, and what they actually meant. The Latin names are generally similar (teredona, termes, termite, terredine) with one, lignorum vermes (wood worm), producing the common English name woodworm. At least three "worms" are implied by the various descriptions:

• Woodworm (teridine, teredona), the most common, as a worm that drills through and/or eats wood
• Shipworm (teredo), not actually a worm but a marine bivalve mollusk
• Termite (termites), a name used by Thomas of Cantimpré, but which literally interpreted means "branch"

The most general name "woodworm" is used here.

The larva of several species of beetle are known as "woodworm". These larva bore into wood, preferring damp and rotting wood.

In modern taxonomy, Teredo navalis is a species of shipworm (Teredinidae family), which is a marine bivalve mollusc that bores into wood immersed in sea water, by using a pair of tiny shells at one end of its body to "gnaw" at the wood.

Termites are winged insects that have their common name from the Latin word termes, which refers to woodworms. Other than the amiguous use of the Latin word termites by Thomas of Cantimpré, termites as such do not appear in medieval encyclopedias.