1. Any of various cold-blooded, usually smooth-skinned vertebrates of the class Amphibia, characteristically hatching as an aquatic larva with gills and then transforming into an adult having air-breathing lungs. Frogs, toads, salamanders, and caecilians are amphibians.
2. An animal capable of living both on land and in water.
3. An aircraft that can take off and land on either land or water.
4. A tracked or wheeled vehicle that can operate both on land and in water.
[From New Latin Amphibia, class name, from Greek, neuter pl. of amphibios, amphibious : amphi-, amphi- + bios, life; see gwei- in the Appendix of Indo-European roots.]
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