A worm is a small, tube-shaped invertebrate with no arms or legs. The worms that hang out in your garden are very helpful, keeping the soil rich and fertile.
Worm can be a contemptuous term for a weak person — and while most worms cause us no harm at all, there are dozens of worms that we'd be better off avoiding. Many worms are parasites, feeding on their host's body. Intestinal worms get into a human or animal's digestive system and make them sick. As a verb, to worm is to move or wriggle with difficulty: "Everyone glares as she worms her way up to the front of the line."