Real Dictionary

amphibian
countable noun: Amphibians are animals such as frogs and toads that can live both on land and in water.
countable noun: An amphibian is a vehicle which is able to move on both land and water, or an aeroplane which can land on both land and water.

amphibian in American English
any of a class (Amphibia) of coldblooded, scaleless vertebrates, consisting of frogs, toads, newts, salamanders, and caecilians, that usually begin life in the water as tadpoles with gills and later develop lungs
of amphibians
adjective: belonging or pertaining to the Amphibia
noun: any cold-blooded vertebrate of the class Amphibia, comprising frogs and toads, newts and salamanders, and caecilians, the larvae being typically aquatic, breathing by gills, and the adults being typically semiterrestrial, breathing by lungs and through th

amphibian in British English
adjective
noun: any cold-blooded vertebrate of the class Amphibia, typically living on land but breeding in water. Their aquatic larvae (tadpoles) undergo metamorphosis into the adult form. The class includes the newts and salamanders, frogs and toads, and caecilians