(1):

(n.) A sea god in the service of Neptune who assumed different shapes at will. Hence, one who easily changes his appearance or principles.

(2):

(n.) A genus of aquatic eel-shaped amphibians found in caves in Austria. They have permanent external gills as well as lungs. The eyes are small and the legs are weak.

(3):

(n.) A changeable protozoan; an amoeba.