1.  Undines are elemental spirits of Water.

2.  undine [G. undine or F. ondine, fr. L. unda, a wave, water.] 1. One of a class of fabled female water spirits who might receive human souls by intermarrying with mortals;--so called by Paracelsus, who conceived them as the elementary beings of water. 2. [cap.] (German pronunciation, oon-dee-neh) Such a being, the heroine of a romance of this name by De la Motte Fouque'. She was a changeling in the hut of a fisherman, where Sir Huldbrand fell in love with her and married her. But he soon neglected his wife for the lady Bertalda, and Undine was carried away by her sisters into the sea. She returned on the day of her husband's wedding with Bertalda, and gave him a fatal kiss.