Real Dictionary

tadpole
countable noun: Tadpoles are small water creatures which grow into frogs or toads.

tadpole in American English
the larva of certain amphibians, as frogs and toads, having gills and a tail and living in water: as it matures, the gills usually are lost and legs develop
noun: the aquatic larva or immature form of frogs and toads, esp. after the development of the internal gills and before the appearance of the forelimbs and the resorption of the tail

tadpole in British English
noun: the aquatic larva of frogs, toads, etc, which develops from a limbless tailed form with external gills into a form with internal gills, limbs, and a reduced tail