tadpole

noun

1. the aquatic larva or immature form of frogs and toads, especially after the development of the internal gills and before the appearance of the forelimbs and the resorption of the tail.

noun

1. 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

n.c.1400, from tadde “toad” (see toad) + pol “head” (see poll (n.)).