1. A cold-blooded, smooth-skinned vertebrate of the class Amphibia, such as a frog or salamander, that characteristically hatches as an aquatic larva with gills. The larva then transforms into an adult having air-breathing lungs.
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.]

The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.