The Collaborative International Dictionary of English v.0.48:

Cutworm \Cut"worm`\ (-w?rm`), n. (Zool.)
   A caterpillar which at night eats off young plants of
   cabbage, corn, etc., usually at the ground. Some kinds ascend
   fruit trees and eat off the flower buds. During the day, they
   conceal themselves in the earth. The common cutworms are the
   larv[ae] of various species of Agrotis and related genera
   of noctuid moths.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Caterpillar \Cat"er*pil`lar\, n. [OE. catyrpel, corrupted fr.
   OF. chatepelouse, or cate pelue, fr. chate, F. chatte,
   she-cat, fem. of chat, L. catus + L. pilosus hairy, or F.
   pelu hairy, fr. L. pilus hair. See Cat, and Pile hair.]
   1. (Zool.) The larval state of a butterfly or any
      lepidopterous insect; sometimes, but less commonly, the
      larval state of other insects, as the sawflies, which are
      also called false caterpillars. The true caterpillars have
      three pairs of true legs, and several pairs of abdominal
      fleshy legs (prolegs) armed with hooks. Some are hairy,
      others naked. They usually feed on leaves, fruit, and
      succulent vegetables, being often very destructive, Many
      of them are popularly called worms, as the cutworm,
      cankerworm, army worm, cotton worm, silkworm.
      [1913 Webster]

   2. (Bot.) A plant of the genus Scorpiurus, with pods
      resembling caterpillars.
      [1913 Webster]

   Caterpillar catcher, or Caterpillar eater (Zool.), a bird
      belonging to the family of Shrikes, which feeds on
      caterpillars. The name is also given to several other
      birds.

   Caterpillar hunter (Zool.), any species of beetles of the
      genus Callosoma and other allied genera of the family
      Carabid[ae] which feed habitually upon caterpillars.
      [1913 Webster]

WordNet (r) 3.0 (2006):

cutworm
    n 1: North American moth whose larvae feed on young plant stems
         cutting them off at the ground