Definition of: amphibian

(am·fib′ē·n) noun plural ·bi·ans or ·bi·a (def. 1)
1. Any of a class (Amphibia) of coldblooded vertebrate organisms with smooth, moist skin, whose life cycle typically comprises tadpoles which hatch from eggs as aquatic, gilled, limbless forms and which metamorphose into terrestrial air-breathing adults with four limbs, as frogs, toads, newts, salamanders, etc.
2. Any amphibious organism.
3. An airplane constructed to rise from and alight on either land or water.
4. A craft capable of self-propulsion upon land and upon water.
—adjective Amphibious.