Pronunciation: (am-fib'ē-un),[key] —n. 1. 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 the moist, glandular skin.
2. an amphibious plant.
3. an airplane designed for taking off from and landing on both land and water.
4. Also called amtrac. a flat-bottomed, armed, military vehicle, equipped with both tracks and a rudder, that can travel either on land or in water, used chiefly for landing assault troops.
—adj. 1. belonging or pertaining to the Amphibia.
2. amphibious (def. 2).