amphibian

am·phib·i·an

noun \-bē-ən\

Definition of AMPHIBIAN

1

: an amphibious organism; especially : any of a class (Amphibia) of cold-blooded vertebrates (as frogs, toads, or salamanders) intermediate in many characters between fishes and reptiles and having gilled aquatic larvae and air-breathing adults

2

: an amphibious vehicle; especially : an airplane designed to take off from and land on either land or water

— amphibian adjective

Origin of AMPHIBIAN

ultimately from Greek amphibion amphibious being, from neuter of amphibios

First Known Use: 1835

amphibian

noun    (Concise Encyclopedia)

Any member of a class (Amphibia) of cold-blooded vertebrate animals that includes more than 6,200 species in three groups: frogs and toads (order Anura), salamanders (order Caudata), and caecilians (order Gymnophiona). Probably evolved from certain fish species of the Early Devonian Period (416–397 million years ago), amphibians were the first vertebrates to move from an aquatic environment to land. Most species have an aquatic larval, or tadpole, stage that metamorphoses into a terrestrial adult, but a few species spend their entire life in water. Amphibians are found worldwide, the majority in the tropics.