Source : Webster's Revised Unabridged Dictionary (1913)

Amphibious \Am*phib"i*ous\, a. [Gr. 'amfi`bios living a double
   life, i. e., both on land in water; 'amfi` + bi`os life.]
   1. Having the ability to live both on land and in water, as
      frogs, crocodiles, beavers, and some plants.

   2. Pertaining to, adapted for, or connected with, both land
      and water.

            The amphibious character of the Greeks was already
            determined: they were to be lords of land and sea.
                                                  --Hare.

   3. Of a mixed nature; partaking of two natures.

            Not in free and common socage, but in this
            amphibious subordinate class of villein socage.
                                                  --Blackstone.

Source : WordNet®

amphibious
     adj 1: relating to or characteristic of animals of the class
            Amphibia [syn: {amphibian}]
     2: operating or living on land and in water; "amphibious
        vehicles"; "amphibious operations"; "amphibious troops";
        "frogs are amphibious animals" [ant: {aquatic}, {terrestrial}]