- any of numerous elongated, snakelike marine or freshwater fishes of the order Apodes, having no ventral fins.
- any of several similar but unrelated fishes, as the lamprey.
- any teleost fish of the order Apodes (or Anguilliformes), such as the European freshwater species Anguilla anguilla, having a long snakelike body, a smooth slimy skin, and reduced fins
- any of various other animals with a long body and smooth skin, such as the mud eel and the electric eel
- an evasive or untrustworthy person
