n pl 1  :  a class of subphylum Vertebrata comprising forms (as the frogs, toads, newts, and salamanders) that are intermediate in many respects between fishes and reptiles, are cold-blooded with nucleated red blood cells and a 3-chambered heart, and that have gilled aquatic larvae and air-breathing adults  2  :  the members of the class Amphibia am*phib*i*an n or adj 
 
 
 
Published under license with Merriam-Webster, Incorporated.  © 1997-2024.