Source : Webster's Revised Unabridged Dictionary (1913)

Amphibian \Am*phib"i*an\ (-an), a. (Zo["o]l.)
   Of or pertaining to the Amphibia; as, amphibian reptiles.

Amphibian \Am*phib"i*an\, n. (Zo["o]l.)
   One of the Amphibia.

Source : WordNet®

amphibian
     adj : relating to or characteristic of animals of the class
           Amphibia [syn: {amphibious}]

amphibian
     n 1: a flat-bottomed motor vehicle that can travel on land or
          water [syn: {amphibious vehicle}]
     2: an airplane designed to take off and land on water [syn: {amphibious
        aircraft}]
     3: cold-blooded vertebrate typically living on land but
        breeding in water; aquatic larvae undergo metamorphosis
        into adult form