Source : Webster's Revised Unabridged Dictionary (1913)

Hag \Hag\, n. [OE. hagge, hegge, with, hag, AS. h[ae]gtesse;
   akin to OHG. hagazussa, G. hexe, D. heks, Dan. hex, Sw.
   h["a]xa. The first part of the word is prob. the same as E.
   haw, hedge, and the orig. meaning was perh., wood woman, wild
   woman. ?.]
   1. A witch, sorceress, or enchantress; also, a wizard. [Obs.]
      ``[Silenus] that old hag.'' --Golding.

   2. An ugly old woman.

   3. A fury; a she-monster. --Grashaw.

   4. (Zo["o]l.) An eel-like marine marsipobranch ({Myxine
      glutinosa}), allied to the lamprey. It has a suctorial
      mouth, with labial appendages, and a single pair of gill
      openings. It is the type of the order Hyperotpeta. Called
      also {hagfish}, {borer}, {slime eel}, {sucker}, and
      {sleepmarken}.

   5. (Zo["o]l.) The hagdon or shearwater.

   6. An appearance of light and fire on a horse's mane or a
      man's hair. --Blount.

   {Hag moth} (Zo["o]l.), a moth ({Phobetron pithecium}), the
      larva of which has curious side appendages, and feeds on
      fruit trees.

   {Hag's tooth} (Naut.), an ugly irregularity in the pattern of
      matting or pointing.

Source : WordNet®

Myxine glutinosa
     n : typical hagfish