living or able to live both on land and in water; belonging to both land and water.

Also, amphibian. capable of operating on both land and water

amphibious vehicles.

of or pertaining to military operations by both land and naval forces against the same object, esp. to a military attack by troops landed by naval ships.

trained or organized to fight, or fighting, on both land and sea

amphibious troops.

combining two qualities, kinds, traits, etc.; of or having a mixed or twofold nature.