The Collaborative International Dictionary of English v.0.48:

Earthworm \Earth"worm`\, n.
   1. (Zo["o]l.) Any worm of the genus Lumbricus and allied
      genera, found in damp soil. One of the largest and most
      abundant species in Europe and America is L. terrestris;
      many others are known; -- called also angleworm and
      dewworm.
      [1913 Webster]

   2. A mean, sordid person; a niggard. --Norris.
      [1913 Webster]

WordNet (r) 3.0 (2006):

earthworm
    n 1: terrestrial worm that burrows into and helps aerate soil;
         often surfaces when the ground is cool or wet; used as bait
         by anglers [syn: earthworm, angleworm, fishworm,
         fishing worm, wiggler, nightwalker, nightcrawler,
         crawler, dew worm, red worm]